Ultra long wall of text that could very possibly be boring to you. If it is, move on and don't flame. Or... as usual, feel the wrath of me ignoring you. Grr. And this is my
personal take on the song. I'm not trying to explain your
point of view. If you feel differently, I'd be more than happy to hear you out too.
I will be refering to Xi Yao and Xue Jian as two separate entities, because, well they are. Xue Jian shared Xi Yao's form, but Xi Yao didn't experience what Xue Jian did (and vice versa).
(Love has not come, and the winds and clouds suddenly changed between heaven and earth.)
The above applies to both couples (plus Long Kui) in general. In the beginning, there was no love between all the characters, but the gears for all the following events were set in motion.
(People with love and loyalty all want to come back.)
Then, the fruit of the Heavenly Tree came back as Xue Jian. She met with Fei Peng, who came back as Jing Tian. Zi Xuan met with Xu Chang Qing (who was originally Gu Liu Fang, and then Lin Ye Ping). Long Kui came back as... uh... Long Kui to meet Jing Tian.
(Love will come eventually, those who are destined to love will in their next lives.)
Again, both couples (plus Long Kui) in general. They were destined to meet and fall in love. So... they did, in this life (which are the next lives of their past lives).
(We have waited for too long, and our tears are dry from crying exasperatedly.)
This could apply to Xi Yao, whose longing made her create Xue Jian from the fruit of the Heavenly Tree. It can also apply to Zi Xuan, because, well... she had a long life, and she was the one who was waiting for Chang Qing (and his previous incarnation). I personally feel that it doesn't apply to Chang Qing, because he was reincarnated twice. After reincarnation, his memory became latent, so he felt no longing until it was jolted. It probably applies to Long Kui too.
(She came from the trees, chasing after the love from her past life...,)
This most probably applies to Xue Jian. Yep. Unless there was some forest chasing I do not remember, in which case this would apply to more females.
(...having firsthand experience of the passing of spring and coming of autumn.)
Long Kui, Zi Xuan and Xi Yao again. They both experienced time passing without their loves firsthand.
(At the extremity of love, even black hair becomes thick and white.)
It could be my failing memory, but I don't really recall anyone's hair turning from black to white. If you remember, please feel free to remind me. However, this could also mean Long Kui, Xi Yao and Zi Xuan witnessing their lovers aging and dying. Although I don't remember Fei Peng and Liu Fang's incarnations living to become old.
(After the sword becomes human, her heart trembles; and the flowers bloom beautifully)
Long Kui, obviously. And I personally think the flowers in the lyrics refer to the love she has for Jing Tian. Or her abilities as 'Red Kui'. But I prefer to think of it as the former.
(Lifetimes are caught up in love and hate, but still...)
(...the steadfast belief exists at the bottom of my heart for you...: )
This probably refers to Long Kui, Zi Xuan, Xi Yao, Jing Tian and Chang Qing. Less on Xue Jian, because although she is considered an incarnation of Xi Yao, it didn't appear that she knew of Xi Yao's feelings, unlike Chang Qing (who actually did have the memory of being together with Zi Xuan).
(Now matter how long the road, it cannot stop me...)
(...from feeling your warmth without distance once more.)
Well, they got together (as in met and had wonderful experiences with each other) in the end, eh? So the determination shows. However, this most applies to Long Kui and Zi Xuan, who was most actively searching for Jing Tian and Chang Qing. It could also apply to Xue Jian and Jing Tian, but the couple was more lucky (or as some people might call it, fated).
(Freedom is lost from these lifetimes.)
Zi Xuan and Long Kui, most likely. One was trapped in the evil sword (for a thousand years), and the other was Nu Wa's descendant (cursed with a long life). Although, another way to see it might be that fate controls everything, so there is no freedom in the world.
(Not knowing to embrace love when we have it, we missed the deepest love.)
Chang Qing and Zi Xuan, very likely. They were more in denial than Jing Tian and Xue Jian. However, it could apply to the latter as well. Long Kui... uh... couldn't
do anything with Long Yang (that's Jing Tian's previous incarnation, in case anyone forgot), so that's... uh... too bad. Maybe in a Japanese fan-made game lol.
(First giving a sword of blessing, then assisting from behind the scenes.)
I'm going to award this to cameo people, Xiao Yao and Sheng Gu. And supporting roles Chong Lou and Mao Shan. The sword of blessing could also be interpreted as a surge of well wishes/help. However, in the literal sense, it would be most applicable to Long Kui (helping with swords twice).
(Fearing there will be no future, we unwittingly left a path of retreat.)
Chang Qing and Zi Xuan, most probably. Because they feared the future (or lack thereof), they chose to give up their love in the end.
(These memories last three-lifetimes-long,)
Zi Xuan and Chang Qing, as a couple. Chang Qing's memory might have been latent, but it was there. Zi Xuan was alive, so... uh... yeah. Xi Yao too, having to watch everything from above. Not Xue Jian, because she's just the product made from the blueprint. Not Jing Tian, because he was not in love with Xi Yao or Xue Jian when he was Fei Peng and Long Yang. Long Kui would almost qualify, but first of all, she loved Long Yang like a brother (unless you have a Japanese mindset...). Even if you do count that, that's only two. So close, eh?
(and has to be forgotten with a bowl of water at the end of it all.)
Come on, this one is too obvious. Chang Qing and Zi Xuan, of course! *throws confetti around for everyone getting the right answer* Although, technically, there were no bowls involved, only leaves...
(After a thousand years of loneliness, you saw the sun once again.)
(But yet again, you turned around and threw yourself into a sea of flames, becoming a phoenix.)
Long Kui. Tada. I would say Xi Yao and Zi Xuan, but they weren't sealed somewhere; neither did they jump into the fire. And the nitpicker in me would ask,'Where's the phoenix you're talking about, lyricist?'
(Trapped by love for lifetimes...,)
(...fresh injuries are inflicted upon old injuries, making them twice as painful.)
Zi Xuan. She's the one who's trapped in the hat trick of love-fests with Chang Qing (and his previous incarnations). Also could apply to Chang Qing, but less. He has rest periods between memory jolts, whereas Zi Xuan has to live with it from Day One.
(Unable to last until daybreak, I am alone.)
(Let starlight take my place by your side on your long journey.)
I'm assuming daybreak to be metaphorical, meaning the blossoming of love. This would apply to Jing Tian (because in the show, he was going to go bye bye soon). However, this could also apply to Chang Qing and Zi Xuan (because they have to let go of each other to go own their own separate paths before their love bore fruit).
(We have been systematically reincarnating for lifetimes, and...)
(...completely letting go will allow us to end an eternity of dependence.)
The second sentence could be taken either positively or negatively. So they will either be co-dependent forever, or end their co-dependency once and for all. Jing Tian would say this to Xue Jian (for her to accept his 'going away' better); and Zi Xuan and Chang Qing would say it to each other (to end the painful cycle of love and reincarnation).
(Whether we are heroes in turbulent times, or living an ordinary dream...)
(...love will not abandon love, keeping these emotions alive.)
This is the conclusion: Love is amazing! Love is great! Love is for everyone, hero or man-in-the-street! Don't let go of the feeling of love!
So that ends my lengthy (and boring, I'm pretty sure) analysis of the song.