Indecisiveness is a common problem. To become confident about your decisions, you have to start taking decisions rather then escaping out or postponing. Every time you will not go wrong. Positive decisions will surely boost you up. You need not to keep analyzing your decisions, which will make you weak. You may go wrong some time but you will learn in process. That is what we call experience. You may discuss with sensible people surrounding you, this will help in making decision.
To ease your decision-making in case of life partner, make a list of qualities that you require in your life partner. See how much that girl fits into it. If you are satisfied by your criteria, go ahead.