Confidence is a big issue in graduate school. Many graduate students suffer from “imposter syndrome”. This may not be so easy for everyone to overcome, but here are my suggestions for steps in that direction.
Apply to literally everything. In January, I had no awards, had never been to a conference, and no fellowships. I felt like I would be easily out competed. I made it my new year resolution, and as of today, I have 5 travel awards and presented at 3 conferences. (Check out my post on fabric posters!) Hopefully a fellowship will soon follow. Regardless, my confidence has greatly improved!
This has been the biggest boost to my confidence, and the key component to my decreasing levels of imposter syndrome. Since I felt like a crappy student, I made it a point to never turn down an opportunity. (Well, I did avoid applying for awards etc until this year, so I was not incredibly self aware). Due to this, I am currently working on 7+ projects. But I have completed 5! And I will most likely complete these as well. Being useful and valued by colleagues and collaborators is a good, non emotion based way to help you view your scientific worth objectively. And lastly:
As a computationalist studying under an experimentalist, I have been exposed to collaborations my entire career. I was surprised to find that many graduate students hesitate to collaborate. It is not scary! You are dealing with a scientist, who values knowledge and research just like you. Degrees do not make that much difference in someone’s personality. (See my post on proposing a collaboration here).