advice sought on endurance in cash.

[Tomcruise]

I've switch from donkaments over to cash (6max 2/4nl) early in sept and i have beat it at a pretty good clip. (was a pretty respected donkament player on ftp, won basically all their bigger tourneys at least once)......anyways...to my question.....often time I don't play sessions longer than 1-1.5 hours, esp. after Im up a buy in or two at some tables....i know this really isnt optimal (considering some of the succesful hsnl players that log some long sessions)....but there is something about taking the money off and walking away for hour or two that makes me feel good>....though i know im giving up profits.....i realize this more of a physchololgy post, but i thought id post it here and see if i get any feedback thanks.