Sometimes you calculate absolutely nonsense

Apr 27, 2017, 2:03 AM |
Here is a puzzle from Emms book where i tried hard to solve and finally haven't solved it:
White mates in three.
Sometimes it happens to me that i calculate with impossible moves (here it was 2... Ke8) or with pieces on their original place when they have moved somewhere else or are not on board any more. I have to keep an eye on that.
Any idea how to fix that?