system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do I think something is a good idea when I am in bed at night, but when I wake up the next day I am too nervous to do it or think it wont work out?
gpt
Everything your brain does requires energy, including "nothing." Specifically, to stop yourself from having certain types of thoughts (let's call them "dumb ideas"), other parts of your brain capable of critical thinking, evaluation, scenario modeling & if-then extrapolation have to exert metabolic energy. Late at night, when you're tired, your brain has quite a bit less energy, and that means less energy for inhibitory functions. 

That means your thoughts are freer to wander haphazardly, following their own chains of association without anyone trying to fact-check them, edit for decency or obscenity or simple shame. This can be "bad" but it can also be good to have "dumb ideas." For one thing, you might learn something about yourself and how you "really" think when the scolds of logic and morality let down their guard. For another, they said the pacemaker was a "dumb idea," etc.