Respect for your own decisions is the foundation of your confidence.
Your decision is the choice you make when faced with alternatives that have logically similar risks and benefits. Decisions are always based on gut feel. When you make a decision you choose an alternative together with its benefits as well as risks.
However, once the decision is made, many of you start getting uncomfortable with the risks associated with your own choice. You also start regretting the benefits (of other alternatives) that you gave up as a result of your decision. This is normal and expected since the alternatives were logically similar in risks and benefits. This leads to post decision dissonance and the associated discomfort and lack of confidence.
You need to respect your decision once you have chosen the alternative and avoid thinking about the other alternatives. Don't forget that the other alternatives had their own risks, as evaluted by you before taking the decision.
Have faith in your gut feel and respect your own decisions. Don't look back once the decision is made. This simple practice will dramatically improve your confidence and effectiveness.