I've never considered myself good enough to play in concerts. I did occasionally at college, but I always found it immensely stressful. Mostly, I didn't feel the same stress in exams - but the effort required to get 3 pieces up to exam standard was enormous.
When I witnessed Andras Schiff performing the entirety of Bach's preluded & Fugues in two 2-hour sittings, admittedly a year apart, I wonder, firstly, how he is capable of memorising so much music and, secondly, how he keeps so many pieces concert-ready. I'm actually a pretty reasonable memoriser. When I did my diploma, I played the whole of Beethoven's Pathetique sonata from memory and I'm pretty sure that I could have played the Bach prelude & Fugue as well, but my teacher advised me not to. Between them I suppose they represent about 20 minutes' music and they were the produce of 2 years' work. Well, more, to be honest, as I'd learned the p & f years earlier, and the sonata. I polished them up for the exam. The one "new" piece that I learned especially for the exam was a Brahms intermezzo and I totally ballsed it up.