I voted for Brexit and for Britain to leave the EU. I'm embarrassed that I believed the claims the Britain would be stronger financially with Brexit.
Why are you now embarrassed by your vote?
Because Brexit is not making anything better financially for Britain and I feel like a fool for believing that it would
It's good when you can admit that you were wrong or when you have changed your mind. We all make mistakes and the important thing is that you learn from that mistake and try to make better decisions moving forward.
I don't think Brexit will be any good for me in the future.
That may be the case, and there may be little that you can do about it.  However, if you are willing to do so, you might try to show others that Brexit is not working.  Then, together, you can try to vote for politicians who will alleviate the problems.