Without measurement, there is no way to ascertain progress.
A few years ago, I had a mentee who came to me saying that she was not doing well at her work. She was scared that she was not pulling her weight and that her teammates had to compensate for her. I asked her to collect feedback from her team on her performance as it would be the first step to know what she could do better.
When I met her after a week, she was beaming. Her teammates had told her that she was doing really well, much better than what they expected from someone with her experience. Apparently she had been comparing herself with much more experienced colleagues and was beating herself up for no reason. I was invited to her performance review where her teammates gave her glowing commendations on the amazing work she had done.
By not measuring (or worse, not having a way to measure) progress, we subject ourselves to avoidable stress. If you are in this position, try to find out how can you measure it. You can ask your colleagues for help too. And if you are seeing someone go through this, reach out to them.
Everyone needs help sometime.