Riverwalk I enjoyed art at school and was, I thought, quite good at it. But I got a very average mark in my English GCE and, hugely disappointed and discouraged, decided I did not have enough ability to warrant continuing to A Level.
I have done several one-day courses but, up until the last couple of years, that was all. I now go to a class one morning a week and have found it has motivated me to do much more at home and to try out new materials and techniques.
Don't let seeing other people who you feel are far better than you discourage you from carrying on. Like anything else, it takes time and practice to improve. Successful athletes, writers, actors, singers, etc, etc, didn't get to where they are without practice. One lady in particular in our class has improved hugely over the last couple of years and that is down to her own self-belief and perseverance.
If you enjoy it, do it just for the love of it and I feel sure you will be surprised at how much you will achieve.
(There are also monthly free drawing and life drawing sessions at the National Portrait Gallery and there also used to be sessions at the National Gallery but I don't know if they still do them).