Lots of us vape and drink 2 or 3 cups of coffee in the morning.
12mg juice isn't a really high level, but that's dependent on your system. If you are quitting smoking, it's probably good to have higher nic. Lots of us started at 24mg and weaned down to 6mg or 3mg over time.
Drink a lot of water during the day. It helps to flush the bad stuff and balance the electrolytes in your system. Get enough exercise to ease stress. Get away from the keyboard, go outside, breath lots of fresh air, and enjoy connecting with nature in your own yard. It's a wonderful way to take your mind off things that cause stress in your life.
Water: How much should you drink every day?