Given the level of mystery surrounding his death, there will always be those who wonder, disagree, and theorize about it.
Sad but true. I've been working on Rocket Dive, Pink Spider, and Ever Free today, comparing different translations and then translating those specific verses in question myself. It's interesting how much is left to interpretation when translating Japanese. The nature of the language is such that you can be as literal or cryptic as you wish to be - to a much more... extreme degree than in English.
At any rate, I am convinced that hide had bipolar disorder. Those three songs primarily deal with the same theme: escapism from one's circumstances. They all share the notion of being in undesirable circumstances: the monotony of life referenced at the beginning of "Rocket Dive", the social stigma attached to creativity in "Ever Free" (How much does love cost? Can you eat a dream? (My) dreams were called nonsensical...) and the 'web of lies' concept of Pink Spider.
In all three songs, the protagonist longs to break free from his metaphorical bonds of captivity, whether professional, social, or psychological, etc. My theory is between the time that "Rocket Dive" was released in January and the following May, at some point he realized that death itself was the only way to truly escape his circumstances.
As for his *specific* problems, well, this mystery to all of us. My guess is that X Japan's breakup had something to do with this. It's absurd to suggest that it didn't. As we know, hide experienced much difficulty in his early life. In X, he found his niche, his place in the world. He felt like he had a purpose, at last. Once this was torn away from him, he must have felt some kind of desperation. He either needed to re-establish himself, reach higher grounds, etc ... or it was all over.
"Rocket Dive" is written from a much more optimistic and empowered perspective than the other too. In this song, hide was clearly unhappy with his situation, but felt that he could overcome it. Through the lense of my theory, it seems as though he was experiencing the omnipotence associated with the "manic" phase of bipolar disorder.
"Pink Spider" seems like a response to "Rocket Dive". He was clearly no longer in the same optimistic mindset that had inspired Rocket Dive. I believe that Pink Spider is a reflection on how he arrived at this point. During his time in X Japan, he was a spider, trapped within a scheme which he thought was the whole world. Everything came to him with ease (as a spider's prey arrives naturally at his web) and the world (which he knew) was at his mercy. But this was all lies.
His solo career (most likely prompted by whoever this "bird from heaven" refers to, whoever his inspiration was...) was essentially an attempt to "fly with borrowed wings". This building off of PanthereNoire's theory... Perhaps his act of killing the butterfly, not out of hatred, but just because he had no wings, is an allusion to how hide destroyed the relationship between Yoshiki and Toshi, and subsequently X itself.
Do I personally think that hide destroyed X? Absolutely not. Yoshiki became stagnant after Art of Life, his magnum opus, was achieved. This is my firm belief.
However, this does NOT rule out the possibility that hide blamed himself in some way. (I need to find a citation for this) but if I remember correctly, hide made some comments along the lines of "X would be forgotten if one of their members didn't die."
The rest of the song is fairly straightforward. His flight on borrowed wings failed (at least in his mind) and all he caught were glimpses of the sky. He tries to fly once again - but this time, I think its an allusion to death - which in hide's mind, seemed to be the only escape.
"Ever Free" is probably the most overtly depressive of all three songs. It's not nearly as cryptic as "Pink Spider". In Ever Free, hide pretty much blatantly alludes to his loss of passion, his frustration with how society views his "dreams", the realization that his days were coming to an end, etc.
It's actually interesting - hide often discusses very solemn themes, but injects this content matter into joyful music! Hi-Ho, Misery, and Ever Free are just a few examples. This phenomenon may actually be a projection of his character: yes, he'll smile for the camera and act charming and charismatic, but inside, the only thing he feels is sorrow. Similarly these songs are very mirthful on the surface, but the lyrics (the SUBSTANCE) seem very desolate. This is one of the most obvious reasons that saying that "hide was happy, there's no way he'd intentionally kill himself" is utterly absurd!
Anyway, this is just scratching the surface, a momentary stream of conciousness, if you will. I have infinately much more to say on the subject, but alas... I have papers to write and time is a salacious jezebel, if you know what I mean ;p