Here's the situation, maybe you can relate.
You're sitting in a classroom, boardroom, etc..., full of peers. All of you had a rigorous application process and all of you made it. BUT, you're sitting there full of self doubt and thoughts that you don't deserve to be there, you're not good enough.
Sounds a lot like imposter syndrome, that doubt in your abilities, you feel like a fraud.
Now that we've established you're human, here are 3 things you can do. For on full week, everyday, try these...
Establish a morning mantra. (or evening or middle of the day, just do it) This mantra can be two or three words or a phrase, whatever is easier for you to remember. Say these words everyday, out loud, while looking at yourself, at your assigned time, without fail.
Take 5 minutes/day, for mindfulness or guided meditation that focus on breath. YouTube has hundreds, if not thousands of them but make it worth your while. Find a voice that is soothing to you.
Stand big and tall! I don't care if you're 5'5", like me, stand up, place your feet a little wider than hips width, bend your elbows and put your hands on your hips. Now stand there for two minutes. (pro tip: recite your manta now)
What does this do? Adopting a conscious attitude, feeling and perception of competence, that you loop continually, will ultimately allow you to embody and become that person you have trained to be.
Fake it till you become it!