How do I make myself feel bad on Yom Kippur for sinning? How do I make myself cry?

Yom Kippur is a festival, you shouldn't feel bad on Yom Kippur, it is not 9th of Av. It is good to cry on Yom Kippur, yet it should come naturally, if it doesn't – that OK. We should be sorry for our bad deeds, regret them and make maximum effort not to make them again The more one learns what is good and what is bad the more he appreciates the need to be sorry for his sins Try to focus on the words of Tfilah, that will keep you busy for most of the day, the rest of it you might find inspiring to read stories about great Jewish people ("a Tzadik in our time" by Simcha Raz is a good place to start) Shana Tova