If I don't like my feelings, my thoughts are to blame. Feelings are simply the readily perceptible side of a thought. Take the feeling, turn it over, and there's the thought.
Feelings coalesce to become moods, states, affect.
The only way to pick part the mood, state, or affect is to wait for the next feeling to come along, ready to drop into the pool of the mood, state, affect, and intercept it: ask it what thought is behind it. Then I can start to sift what I want to allow into the pool and what I want to reject.
The pool is always being drained. If, consistently over time, I allow only the right thoughts (with their attendant emotion) into the pool, the pool eventually clears.