It depends on how tired you are. Also, the balance of how much you're in the state of going to sleep, as well as how much you're aware. Too much awareness and you'll never fall asleep. Too much sleepiness and you'll fall asleep without lucidity. It is successful to those who can easily balance between the two, but if you can't do it that well, then it's not going to be an instant lucid method.

So, it really depends on how well you can accomplish this.