You can expend a morning to jerk off (under the "rest" command), otherwise your best bet is just to suffer through it until you can unlock the dick functions and relieve yourself with Yuna (masturbating on her face or chest) or survive long enough to bang the psycho on the beach during a run.
You can use the crank it function when you have free time in the morning.
Other than that you have to unlock your schlong for night sequences and crank one out to bring the lust back to zero and not lose like 90% of your stamina when you're forced to bust in the morning.
