The Square of the Pawn

Why did I take that stupid pawn? I blame the diagrams. Here's what I mean.

 In the original position I had about 2 minutes left on my clock, so I didn't have much time to calculate a position I didn't fully understand. But I went after that pawn on b7, and lost. Of course. Because it turns out I didn't understand the square of the pawn like I thought I did. And here's why. Notice in the original picture, the square of the pawn? Well, the king is the same distance from the pawn no matter where it is in the square, essentially. So the optical illusion for me that the pawn was somehow closer was due, I think, to the fact that I am used to those pictures that show the pawn so far away in those square of the pawn diagrams. Once I took that pawn on b7 he didn't even need his king near there. C5 and the pawn is passed and my king is outside the square and mine is queening way too slow. I needed to play b4 to prevent c5. But I thought the king was getting to those pawns too quickly and that I couldn't afford the tempo.