I'm not sure how the last four lines clash with the rest of the song. For one, it didn't say what could "happen to you" - it might have been a negative thing all along. The second verse is more akin to "who'd ever thought we'd be so lucky", but it also doesn't say whether it's gonna happen or not - it just says "you'd better believe it".

Actually, to me this is about two things - 1. you don't know what's gonna happen, so don't be so sure (whether you're overly positive or negative), and 2. going along with the "sometimes desire is all that's there" aspect - don't give up beforehand, you better believe it if you're gonna go for it. It's a double edged approach in my opinion (as this also breeds fundamentalism or questionable autosuggestive esoteric "YOU CAN DO IT!"-salesmen-types... I hope you get the picture), but if you break it down to "give it a shot, don't sell yourself short" it's actually in line with the rest of the album's themes (You've Got A Chance, Don't Sell Me Short, Let It Burn...).

This song is directed at anyone who feels alienated by the status quo.
It's a little unclear to me, but I think the message to these people is to expect that burden and believe that you can change it the way things are if you're persistent, have freedom of expression. But then the last four lines seem to suggest that effort to change things would be futile, but this might be BR's famous satire.

This is about being your own person. Waiting for the day when you're out of school, no more junkies only there only because they have to be. It's hard to believe (can't wait for the day when I get into a school where people wan't to learn). The lyric that pieced it all together was "Sometimes desire is all that's there" (think of a Streetkid Named Desire).