What worked for me was to build up gradually over time. I started only napping when I was very tired, in my bed, with the lights off. Even then it took practice

What worked for me was to build up gradually over time. I started only napping when I was very tired, in my bed, with the lights off. Even then it took practice before my body learned to fall asleep in a reasonable amount of time. Then I started napping with the lights on, and then when I wasn't super tired. Today, I can fall asleep quickly in a chair in a noisy office.