Everyone makes mistakes. Well - everyone except the snake. The snake only does exactly what you told it to. That's kind of the problem.
But now your mistakes are not a problem either:
Ctrl + Z undoes your last edit on the canvas. Ctrl + Y brings it back. Up to 20 steps.
Dragging a block is one step, not fifty. Wire it wrong, delete the wrong thing, drop a block in the wrong place - Ctrl + Z, and it never happened.
The snake, sadly, still has to live with whatever it walked into.