Reddit reviews Why We Sleep: Unlocking the Power of Sleep and Dreams

From physical health perspective it impacts our ability to sleep. Many people use it as a crutch to work past chronic sleep deprivation. For people like me even consuming it in the morning will impact my sleep, and by extension my overall health. Book

It also impacts my sense of well being. On coffee I often react with anger in situations where its not appropriate and often counter productive.

All that being said, I still use it as a tool in circumstances where its helpful. I'll use coffee on weekend mornings to to ensure I break my fast at the right time. (assuming there are no coworkers around for me to get angry at.)