In the Howard Roark section--the last part--at the end of chapter 8, Peter Keating and Howard Roark sign their own little contract/agreement to build Courtlandt Howard's way. Keating then shows Howard some of the paintings he's made. Howard shakes his head. Peter Keating always wanted to be a painter, not an architect. His mother pushed him down a road he didn't want to go down. Can anyone explain this last part of the chapter? Is Ayn Rand saying it's too late for Peter to be a great painter?
At this stage of the story, Peter Keating has spent so long betraying his values, and not focusing on what he really wants to do with his life, that he's wasted his prime.
To become a master at something, one must start early and spend lots of time doing it. Peter has started too late ever to become a professional fine artist.
He could perhaps become a fairly proficient amateur, but that's all.
The lesson of this scene of the Fountainhead is that Peter's immoral choices have cost him irrevocably. One might be able to redeem individual poor choices as one lives, but poor choices left unredeemed, and compounded with more and more poor choices, eventually become unredeemable.
Life has no reset button.