Like any other practice (programming, music, art) it can be difficult at first and the benefits take time to accrue. I struggled to sit comfortably for a long t

Like any other practice (programming, music, art) it can be difficult at first and the benefits take time to accrue. I struggled to sit comfortably for a long time before I reached the point where I can sit easily for an hour - though it still takes a little time getting up :) As far as bladders, in the Zen tradition, half-day or full-day sits are short sessions of sitting (maybe 35 minutes) alternated with walking meditation (maybe 5 or 10 minutes). During the walking meditation, you have an opportunity to step out if you need the toilet. Also, there can be a meal and rest period thrown in so that it's not actually 4 or 8 hours of just sitting.