Being less critical is almost as simple as your abc's.
a - activating event
b - belief
c - consequence (sad, happy, angry, frightened)
d - dispute
e - effect
The activating event determines the outcome, but it is our belief that determines the consequence.
If we believe that we are stupid and we make a mistake, we will believe that we have failed because we are stupid.
If we change our belief and see what we are doing as a learning process, we will still be happy. It may not have worked, but because we have changed our belief, we persist and try something else.
If you dont like the consequence, you can dispute it. Then we have an effect, whether desired or not.
So if you find yourself being critical, examine your beliefs about yourself. If you can learn to love yourself and change what you believe about yourself, you will become less critical.