it takes practise. Likely you try and take a nap a few times, it takes too long and so the next day you don't bother. But if you can get through that it gets ea

it takes practise. Likely you try and take a nap a few times, it takes too long and so the next day you don't bother. But if you can get through that it gets easier over time. Your body learns that it's "time to go to sleep". The other strategy is physical and mental exhaustion, for this I recommend starting a business and/or becoming a parent.