Doubts
Doubts vanish when you take deliberate action.
The mind is extremely good at imagining what can go wrong; being cautious has been advantageous evolutionarily — not getting wiped out has always been a winning strategy.
However, the same caution makes us shy away from attempting things we are uncertain about — and those are often the ones that could make our lives better.
Taking action in the face of crippling doubt is the primary way to let go of it.