Two hour naps will likely put you into a deep slow-wave REM sleep cycle. Waking up mid sleep cycle often leads to grogginess. If you cut your naps to 25 minutes

Two hour naps will likely put you into a deep slow-wave REM sleep cycle. Waking up mid sleep cycle often leads to grogginess. If you cut your naps to 25 minutes or slightly less, you avoid deep REM sleep and should wake up feeling refreshed. "Why We Sleep" by Matthew Walker is a good summary on the science behind sleep. The book also recommends to not use the "snooze" function on your alarm clock. It allows you to slip back into a sleep cycle that gets disrupted multiple times everyday.