They take time.
Confidence and research require evidence.
They can be inspiring and could lead you to new ideas.
Confidence and research are processes. Whatever you do today, might not be what helps tomorrow.
As a postgraduate researcher, your confidence is like your research: your responsibility. You have to take charge of it. To make it real you have to act and keep acting.
Make plans for your research, make plans for your confidence. Act to further your research, act to further your confidence.