One of the best ways to keep yourself honest when going over chess puzzles, is to set a timer and write down everything you were thinking. At the end compare to the correct answer. If you have a coach/teacher this information will be invaluable to them, and they can help you clean up how you calculate. A huge difference between titled players and non-titled players is clear & concise calculation.
Links for Tips About How to Get Better at Calculation:
It's time to put 10 minutes on the clock and see what you got!
Black to Play and Win!
Black to play and Survive!
White to play and Finish Black off!