You may be chronically sleep deprived and not realize it. If that's the case you should try sleeping really consistently for a week and check the difference. Don't use an alarm, just be really disciplined about going to sleep early enough to wake up naturally. No caffeine or other stimulants. The difference between a well rested brain and a sleep deprived one is night and day.
I'd add that it's worth spending some money on a decent mattress, great pillows, and tracking just how restful a sleep you're getting. The return on investment will exceed just improving speed of decision making.