Should is a four letter word. Even if it has six letters. “I should” and “I should have” are killers. Remove the word “should” from your vocabulary. “Should” is a big generator of guilt and regret. The less guilt you generate, the less you have to get rid of.
Another big generator of guilt and regret is the phrase “if only.” Remove that one from your self talk as well.
Whenever you find yourself saying, or about to say (to yourself or another), “I should” or “If only”, pause and reframe that. “I can,” “I may choose to,” “I want to.” are all good reframings for should.