Yogi: I’m used to practicing samatha, and when I switch to awareness practice, I often become drowsy.
Sayadaw: You use too much energy to focus when practicing samatha – so, when you relax and change to being aware of multiple objects, you exert less energy and the mind gets sleepy.
In actual fact, you shouldn’t force in concentration practice either – you just need to be patient and be aware again, again, and again. You do this for a long time – the mind wanders off and you bring it back to the target again, again, and yet again. Slowly, the mind stays with the target.