What you are doing is called yoganidra, popularly known as guided meditation. You prepare your body, your mind, relax all your muscles, determine what this sess

What you are doing is called yoganidra, popularly known as guided meditation. You prepare your body, your mind, relax all your muscles, determine what this session is about(relaxing), visualize something that helps you not get distracted and the next thing you know is you are deep into nothingness. And its smart to not stretch it beyond 20-25mins, our single sleep cycle generally is between 90-120mins, of which the first 20-25mins is the a first stages of non-REM sleep(this gets shorter after the first sleep cycle in a way) in which our body is relaxing but our mind relaxing but fairly active. This is light sleep. Beyond this stage we slowly enter into deep sleep stages in which if you wake up you feel very groggy, if you find yourself waking up feeling groggy, its better to finish the complete sleep cycle of ~90mins, like a complete sleep cycles.