There are two desirable things in Mysticism, Sufism, Tasawwuf. Self annihilation in Allah Most High. This is the excellence (ihsan) of submission to the Will of Allah Most High. The oriental phrase is called fana-fillah. Annihilation in God. This is not physical annihilation but spiritual annihilation. Annihilation of your wants, desires, intentions and feelings. The other desirable thing is recognizing Allah Most High (ma-arifat). That is familiarity with the attributes of Allah Almighty. A Person who has achieved this is called an Arif. That is a friend of Allah. This is a high state of enlightenment. We hear people saying that my life experience says that there is a higher power. This person is enlightened. Further progress in that direction will lead to the desire of submitting oneself to this power. Annihilation of personal consciousness into Allah is self annihilation.
Now consider the other possible situation. Suppose you annihilate yourself into Lord Most High without recognizing enough of His attributes? Well you are taking a right step in wrong direction, so to say. You shall end up there but some things will not fit in. This is an intermediate stage towards higher enlightenment. That is the majzoob state. We recognize such people around us. Elders tell us not to disturb such people. And that is meant as a warning. There is no fun here.