I commute 12 miles one way on NYC streets with lots of traffic. I ride 4-6 times a week and totals to over 100 miles a week pretty consistently. Commuting is most of my mileage and I enjoy it. There's flats, hills, downhill (on bridges), nature through Central Park and I get to see different neighborhoods in the city. Its faster than riding a subway and such a great way to workout. Using Strava makes it more fun if you commute-- you can keep track of your performance and know how you've done in various sections. The key is consistency. Keep at it!