No matter how much you progress as a person, chances are you usually feel as though you still have a long way to go and a lot to improve. You are, after all, your own worst critic. There's nothing inherently wrong with wanting to improve yourself, but it's easy to forget how much we accomplish with new goals constantly popping up all the time.
The best way that I've found to keep track of progress or personal evolution is keeping a journal. Though I always have things about myself that I want to work on, reading over entries from a few months ago give me no choice but to accept that I have moved forward from where I was and deserve some credit. Also, it's a great way to organize thoughts or find out how you feel about something. You may feel like you know what you think about everything, but a lot of times without some type of structure our thoughts turn on themselves, start to be cyclic, or wither and die. A lot of times I find my opinion along the way when I'm writing. Something that may seem like a mundane thought at the time(and would've otherwise been forgotten) can be a spark of inspiration when we look back on it a few weeks later. You find patterns in your thinking, consistencies are realized, dots get connected.
Writing shows you that you've got some interesting stuff up there if you just organize it. I learn something each and every time I write, without fail. I have journals dating back to age 10. I've never kept one consistently(until now), but on and off. It is always interesting to review them and see how much I've changed.
Oddly enough, a lot of times you don't realize how many changes you go through until you have a record to put it in perspective. An example of this would be watching a movie you used to love that now seems ridiculous. I read about the things I spent time fretting over at age 14 and laugh aloud. Those entries can be funny, but it's also good to know that had I not written down my experiences at the time, the memories would be gone. I can read pages from 10 years ago and be transported back to that age, day, and mindset. Reading over these pieces of the past give me a holistic view of where I came from.
A good chunk of the writing I've done throughout my life has been when I'm upset about something. It always helps me slow down and get my nerves under control. Writing is very therapeutic. If you're stressed but can't pinpoint why, sitting down to a notebook and getting your pen moving can bring your troubles into plain sight. So start a journal already. You don't have to be a good writer, this is for no one but yourself. And it doesn't matter if you have no clue where to start. I guarantee if you sit down and force some words out you'll find your direction.