Just saw this for the first time this morning. That I can remember, anyway.
I "hear" this as full of polarities (is that the right word?) Feeling great, yet in a funk. Night and day. Working hard for something and throwing it away, brighter lights/darker nights. I especially like the last one: the fall preceding heights. It's the opposite of what I would expect, so it catches me by surprise.
I saw one thing I might change, depending on what you're going for. The word "promise" occurs twice and pretty close together. If you wanted to avoid that, you might say something like, "Swear to me you'll never be dishonest".
That's all I have. And now I have to go look to see if you've posted the final version yet....