Tunnel vision is a relatively common occurance at amateur level. But sometimes, both players can be so tunnel visioned to a same thing that they both miss what they normally wouldn't.
I just played a game where I won pretty handedly in 16 moves... but I realized in post mortem that what I thought was my crushing move was actually a HUGE BLUNDER.
Being tunnel visioned is something that I struggle a lot in my games. It leads to faulty assumptions, not anticipating my opponent's best candidate moves, oversights, and all the bad stuff that you want to avoid. Well, I still need to work on asking myself before each move "is it safe?"