I heard a man once say that he had discovered that whenever he was resentful, it was about not getting his way in the past.
And whenever he was frustrated or angry, it was about not getting his way in the present.
And whenever he was fearful, it had to do with not getting his way in the future.
That rang true to me, and I realized that if it IS true for me, then virtually ALL of my heartache comes from not getting my way, and my reaction to that. So virtually ALL of my problems come from selfishness. Get over my selfish outlook on life, and I get over my problems.
A simple solution. Not always so easy for me to implement.