Do you build up tolerance overnight?

So I’ve been smoking for 3 years every night for sleep issues, I don’t smoke a lot usually it’s just half or one joint a night and it seems that it happened overnight but I can’t get high anymore. One night I was high out of my mind and the next day nothing anymore. It’s been almost 3 weeks and now when I smoke there’s just no effect anymore whatsoever. I can feel a buzz for 5 minutes and then it’s gone. So I was wondering is this how tolerance happens and what’s the best way to reset it?