Hangover

After years of experimentation, Dr. Odd determined that the best remedy for a hangover is not drinking as much the night before.
When he woke with the worst hangover of his life, he built a time machine and went back in time to convince himself not to drink so much.
But instead of convincing himself not to drink so much, he saw how much fun his past self was having, so he got drunk with him.
Both his selves woke up with hangovers.
Failure.
He started to build a time machine.
“Can you do it quieter?” his past self groaned.