I've always found an easy way to write new jokes is go over old notes. We all have them, or at least you better have. Keep those notebooks once you fill them with ideas and scribblings. I have some that are three decades old and believe it or not there are new jokes inside each of them.
Every time I crack one of the old binders it's like a time capsule of thoughts, a comedy diary sorta. I had this habit of dating stuff that I wrote back in the day and so it makes it easier to know where I was (comedy condo, a hotel, comedy club, home) and who I was with when I made some notes or jotted an idea. Worth hanging onto just for that. Some of those dates correspond to a few famous comedy names now, weeks I will never forget.
More fun is coming across the first time i scratched down the idea that later became one of my main jokes or closing pieces. It's like mining and I just found the old gold vein again.
I'm convinced scanning pages within a saved spiral is a great way to rediscover an energy as well. It has been for me at least. The pages hold onto a magic I think. A creation type hocus pocus that affects me for the positive ;)
Keep your old notebooks kids. They will be treasure for certain in the coming years. They'll never stop helping you. An old spiral notebook may just be the greatest example of you helping you YOU will ever possess.