Do without saying, don't say without doing. Underpromise, overdeliver. Don't mention you are working on something until you are confident it can be finished.
You will often feel scared of starting a new challenge, or worried you won't do it properly. Stare directly at the problem until you can move onto the next one.
The three best things you can be are honest, reliable, and decisive.
Throw your phone into your backpack, into another room, just out of sight. The best way to be not distracted is to remove all distractions.
The hardest part is getting started. Once you get started, you won't want to stop.