This is pretty much cognitive behavioral therapy (the empirically best-supported type of psychotherapy). The basic premise: events happen, we interpret those events to mean something, and we have feelings based on our thinking. So by changing the thoughts you have about events, you can change the feelings.

So when an event happens (e.g. I argue with a relative), I get very different emotional yields from different starting thoughts: "She's such an idiot" vs. "I'm a horrible person" vs. "I guess we were both probably stressed about other things, because we don't normally argue like that." CBT is the process of noticing what your irrational or unhelpful starting thoughts are and intentionally substituting more rational or helpful ones until it becomes habitual.