I don’t see a problem with optimism.
Optimism is fine.
The problem here is Trump is delusional. Even the most optimistic Republican operative has entertain the thought that the midterms could be bad. Trump is not even doing that.
The midterms could be "bad", but I doubt that the GOP will lose the Senate, and I really doubt they'll lose the House (although they'll lose seats; that's for sure).
I do believe that the Democrats will elect new Governors in a slew of states and take back a few state legislative houses, holding PA, MN, and CT, and POSSIBLY retaking FL, IA, IL, and GA.
In the end, I predict this will be an election with something for everyone.