Fall back asleep if you can after each attempt (whether successful or not) in order to make another attempt to leave your body upon your next awakening. That way you’ll not only be able to leave your body in one day, but also to do it several times on the very first day!
At a School of Out-of-Body Travel seminar, a novice was able to leave his body for the first time in his life in 6 of 8 attempts upon awakening the very first morning.
Even the most unsuccessful attempt should last no longer than a minute. If nothing happens over that period of time, it’s much more effective to fall asleep and catch the next awakening, as opposed to stubbornly trying to squeeze results out of the current attempt.