In years past, recording yourself was very easy and cheap to do, with the inexpensive cassette recorders that a lot of folks had. Modern technology makes recording almost as easy (but not cheap) by using video cameras or small high-tech audio recorders. Even most digital cameras can take a movie--with sound-- of your playing. But whatever your favorite device is, just record yourself playing a couple of tunes. Then play them back and see what you sound like.
When you hear your music played back, it might not sound quite as good as you thought it was going to. (My band-leading, banjo-playing brother-in-law Mike says that for him, recording music-- and listening to it afterward-- is as pleasant as having teeth pulled. But that's just his opinion.) Now, I'm not saying this trying to discourage anybody from playing. If in the playback, you don't sound like Earl, or Ralph, or J.D., or Murphy, that's not a reason to give up playing, or even recording. The point is that you can really hear what your playing sounds like. You can hear all your notes, and your timing, and your rhythm. And if you are playing steadily enough on the tape to play along with yourself during the playback, that's excellent! You've come a long way, and are ready to play with other people, whether you feel like it or not!
Sometimes when you hear yourself for the first time, you might be discouraged. But this doesn't mean that your playing normally sounds the way it does on the tape. Any time the tape is rolling (or any other recording is going on), you're going to have it on your mind, either consciously or unconsciously. And it might affect your playing. But the more practice you get recording, the better you'll play each time you record, and when it comes time to listen back to the tune, the better you'll sound. Recording and listening is great practice, and can sure help a person's playing!