It may seem obvious but sometimes we just need a bit of faith in ourselves. But there's many ways to have faith in ourselves. Sometimes, it's just to put the self-doubt and negative speak aside and just try and other times it is to have faith in the process. Both seem immense when trying to overcome them.
During my yoga journey I discovered how many asana (yoga poses) I had steered clear of because I didn't believe I could practice them. I didn't even want to attempt some of them; some I was afraid of trying, some I felt I would never be able to do and decided not to bother, others seemed achievable in time, but not "now". Eventually, I told my self doubt to go away and did try them, or versions of them. The photo of me in the 'about' section here was taken not long after doing a headstand (using props) for the first time. Now, I'm not really in the habit of liking photos of myself but, actually, I love that photo. I think I look so happy, because I felt happy, I had achieved something and it felt great. I'm not saying go out and try challenging asana without guidance or assistance from a yoga teacher because, yes, you could actually hurt yourself!! I didn't just "do" a headstand, I had spent a long time working my body toward getting into this and I had my peers and teacher to guide me. I'm still not ready to do a full, weight-bearing headstand, and I may never be ready...but that's OK. I'm happy with my current version, but I'll still work on it and develop it for myself.
I was recently at a workshop and the teacher running it asked how long are you willing to work for a pose? A week? A month? A year? Ten years? These things can take time. There are poses I am working on now, that I will probably still be working towards next year, the following year, or beyond. That doesn't mean, I shouldn't try the pose or versions of them. I have to allow for the time to take what it will take to get there. I MUST be kind to myself on the journey, but I must take that path to get there, even if that means going backwards before I can go forwards again. I once spent a whole day just working on sitting, standing, taking a step backwards and forwards again, working on using specific group of muscles. At the time, that felt like a HUGE step backwards, and it was, however, I needed to spend that time doing that before I could go forwards again. I won't forget that day; I felt quite disheartened by it. Spending that time allowed me to get in tune with these muscles and how they work to support and move my body.
We need faith in ourselves: to take that step and not be afraid to go for it, or to take a step (or many steps) backward before going forward again. Take a breath, and have faith in yourself.