Success can bring a sense of loss, as Joan Bolker eloquently notes in Writing Your Dissertation in Fifteen Minutes a Day:
"How do we deal with the fact that there is sadness as well as joy about each major step we take forward – including finishing a doctoral degree? You may expect that you will feel only relief and pleasure when you earn your degree, so you may be startled by feelings of loss and sadness. Maybe you will grieve that a major stage of your life is over, or perhaps you will mourn the important people who are not alive to witness your triumph, or maybe you'll confront the gap between the dissertation you've actually written and the one you imagined you would write...Every major life change destroys the equilibrium of our lives and our self-image and leaves behind a portion of an old self."
I'm guessing that, for many people, a sense of impending loss is a major, and unrecognized, barrier that's keeping them from completing their current step, or taking the next one.
I'm also thinking about how sometimes you do the right thing and it simply doesn't work out too well. Or, it works out as well as possible but there are loose ends. Or, for whatever reason, you've still got that queasy, unsettled feeling. Whenever you give up a bad habit, or a bad relationship, or anything, it still feels like a loss and you will probably need to grieve. (The practice of nonviolent communications teaches us mourn instead of regret.)
I meet people all the time who took the moral course, the courageous course, or even the only course, and feel confused or guilty because the outcome wasn't 100% happy or clean. In fact, expecting it to be 100% anything is perfectionist. So is expecting yourself to be psychic and capable of perfectly predicting the outcome of an action.
The world is filled with pitfalls, but it's up to you to be the kindest possible nurturer of yourself instead of the harshest judge. It's also a good idea to plan for success so that you're not caught off guard by its shadow side.