This idea is taken from the book “Chess Master...at Any Age" by Rolf Wetzell.
Compile a notebook (word processor file?) containing a list of positions where you went astray or you missed something in you own games. Also, you should give a title to each position. Periodically go through the positions to learn from your mistakes.
Here are two examples from my games:
Keeping the right concentration level in zeitnot
Mora L. – Rozzoni D. Bratto “B” 2007
Black played 37..Re2?? hoping for 38.Qxe2 Nc3 but I lost immediately after 38.Qxd5
Just after I resigned, someone shew me I could have won with 37..b4!!
if 38.Qxd5 Rxd5 -+
if 38. Nf2 Nc3+ 39.Qc3 bxc3 -+
Ferraris F. – Rozzoni D., Milan 2005
Black could have drawn easily with 24..Rxd6! 25.Rxd6 Qg2+ 26.Ke1 Qg3 with perpetual check.
If 26 Ke3?? e4 mates.