Your testosterone (the hormone that is largely responsible for your sex drive) is produced while you sleep. If you have consistently poor sleep, your testosterone levels drop rapidly.
Keep as much artificial light away from your eyes as possible two hours prior to your bedtime. Sleep in as dark of a room as possible, and prioritize getting at least 8 hours of rest per night. Your testosterone production will increase from the improved sleep. The extra testosterone will give your sexual stamina a boost.