The only realistic answer to that question must depend upon whether or not - or to what extent - one is a pianist or not in the first place. Many composers these days are not pianists (including me, sadly), although quite a few do at least have some proficiency at the instrument. If I might speak for my own experience, although I knew that I had not a shred of pianistic talent, I became ever more drawn to the instrument and what it could do; this created the problem as to how I could even begin to write effectively for it as the great pianist/composers did. I think that the piano is probably one of the worst cases in that it's harder to write well for it as a non-pianist than it is with many other instruments. I tried to resolve this dilemma by spending hundreds of hours cooped up in basement practice rooms at college haplessly trying to sight-read my way through sheaves of Chopin, Liszt, Alkan, Busoni, Medtner, Rachmaninoff and others as well as the complete Chopin/Godowsky Studies, the last of which is perhaps about the most absurd thing to try to do when you can't really play the insrument. I don't ever regret the exercise, however - arduous and often frustrating as it was - because it did eventually help at least to give me some kind of perspective on (a) what it must have felt like to be able to play as those composers did and (b) the sense that, for them, the borderline between piano performance and writing for the piano seemed so nebulous as barely to have existed at all.
I don't suppose that this is much help but it's the best that I can do!
Best,
Alistair