ok, maybe i shouldn't post here - i am not a concert-pianist, and i make my living mostly out of teaching (let's say i earn my bread by teaching and playing gets me some ham on it too

). and i have to say i don't think i could cope with a schedule like mihaela ursuleasa's.
however, i think everything is important. in order to be a good instrumentist and musician, you need to be a human being. so, if you psychologically need friends, going out occasionally, watching movies from time to time, posting on pf

), just go ahead and do it. forcing yourself to practice while your mind is going "oh, i wanted so bad to go to this party tonight, but i have to stay practice" makes that practice session useless. go to the party, stay for a couple of hours, have fun and come back to practice relaxed.
as long as you keep your activities well-balanced and you don't exaggerate on either side, everything should be fine.
imho.