Lyric discussion by SoldYourSoul 

Cover art for Tunnelvision lyrics by Here We Go Magic

I hate to be that guy, but I believe this song is about (at least in part) psychedelic drugs. Psychedelics can radically alter your vision, or give you an odd perspective, or warp/curve your vision like a tunnel. "Strange decision" might be referring to the decision to take whatever it was the speaker took. I'd definitely say that's a fitting phrase - I remember when I tried shrooms, I felt very strange the entire time, and wondered why I decided to take them. Looking back on it, I can't say it was a particularly good or bad experience; it was just strange. "You know you want it all:" psychedelics can open your mind to ideas and truths (and a vast amount of sensory information) that seem completely beyond human cognitive abilities. It can be like finding the key to the secrets of the universe ("anything is possible").

The overall ambient/psychedelic feel of the song supports this reading. The lyrics, too, seem to be a bit scattered and meandering, not unlike the thoughts of someone tripping.