Sometimes getting too fixated on a plan, on "what to do next, in the long run", can make you blind to obvious blunders, because you are only looking at your "plan" rather than your piece safety. In my latest game I had this position:
My knight was a bit trapped behind my own pawns, so I was fervently thinking how can I get it unstuck. I was thinking which squares would be better for it, so that it could actually do something. Getting it to c6 and from there to d4 would be ideal, but I couldn't see any easy way of getting it to c6. Another good square would have been e7, attacking the f5 pawn and supporting the g6 square for a possible pawn advance, but I couldn't see an easy way of getting it to e7 either.
Then I thought that my best option would probably be to get it to b6, and from there possibly to a4 and c3 to get behind enemy lines, or alternatively to d7 and from there to f8, to support the g6 square.
So with my plan decided I commenced it, and moved Na8. Approximately half a second later I noticed the problem with that move and resigned.
I was so concentrated on my plan that I was blind to obvious blunders.
As a beginner myself, I had the same question lingering on my mind. Some really helpful ideas and resources in this thread!