Mentally scratched and dented, maybe. Strip the old finish, sand it down a bit, and refinish, and that brain will look just like new.
OP is probably old enough now to accept that everyone eventually dies and becomes forgotten, and it's best to do things for yourself in the present, instead of fueling some invented myth of your own future importance. "Look upon my works, ye mighty, and despair."
Your brain is just dumping different quantities of different chemicals all over itself, and it's making you think you've gone crazy, just because it's different from what you remember from when you were younger. Well, you haven't gone crazy. The same thing happens to a lot of people. You get to a certain age, and your kids become more independent, your parents die, your pets die, your career hits a plateau, and maybe your spouse has some of the same stresses and blames you in some way for them, and that becomes yet another stress. Exercise and diet help balance your brain chemicals, but then again so do prescription drugs, herbal remedies, and recreational drugs. Some people resort to religion or psychedelics or both. Some people start a second batch of kids or adopt or get several cats. Some start to write books or music, or create visual art. Some splurge on luxury goods. There are a lot of ways to try to get back to feeling "normal" again; some actually work, and some are just placebo.
Ultimately, the common factor is that all these people realize that they are mortal, and their time is running out at the rate of one day of life per day on the calendar. They're afraid they're wasting it. But no matter what you do, you're going to die, and then everyone who cared about you or hated you will also die, and it may well be that your greatest accomplishment will be to spend your entire lifetime just propping up a trade economy with tasks that have little meaning when considered individually. But maybe you and the 7 billion other people also doing existentially meaningless grunt work manage to support themselves for species survival, and also collectively put together a colonization mission somewhere other than Earth, and you contributed more than a 7-billionth share of that accomplishment. Hooray for humanity; hooray for you!
If you can't find meaning in your life, just make one up. If it's a bad one, it will be forgotten; if it's a good one, it too will be forgotten. Your memory might last 2 years, or 2000 years, but it won't be you--you will be dead and gone. The important thing is that your chosen meaning motivates you to continue living your life, even when you have become genetically useless to the species and so many of your former peers seem to have gained more social status than you in the same amount of time. You don't need to be great and influential. Just being is enough, and you can be whatever you want to be, instead of someone else's child, or someone else's parent, or someone else's spouse, or someone else's employee.