Who does criticism hurt the most? The one being critical.

Every time you criticize someone, you criticize yourself (for being critical of another). Likewise, anytime you compliment someone, you compliment yourself (for giving the compliment). Strive for a 10:1 ration. For 1 criticism, you give 10 compliments (to yourself or others).

Don't be critical, critique instead! Only point out faults if you can offer suggestions. Unless you can offer suggestions, you have no place pointing out faults.

But don't beat yourself up for being critical either. The best way to stop the loop is to inject a compliment.

All the kind words you say will be forgotten when you say our send words of hate. I have experienced this myself and while I wish I could take back the words I said, I never can. But what I can do is note the bug in my program and use it to run a less buggy program today.

Which words hurt the most? The ones we speak to ourselves. Hurtful words we say to ourself are the precursor of hurtful words we say to others. It's a form of priming.