Unless you take off and try the round trip on day one. Build up to it a bit with some training rides around the neighborhood. It will only take a couple weeks until the 14 miles isn't scary. Then take a saturday or sunday and ride in to work, take a break and ride home. At that point you'll prove to yourself that you CAN do it and you'll be good for daily round tripping.

By the way. Don't worry about the rain, you are going to be wet. Accept that and you don't care anymore.

Have fun.