Like I said in another thread: Riding in the cold is 50% mental and 50% gear. You need the attitude that you're gonna ride regardless (unless it's just plain foolish or dangerous to do so), but you'll be cold if you don't have proper clothes. The coldest temps we've had in NC since I started bike commuting 5 years ago were about 15 F and I was warm enough, altho my water bottle froze solid during the ride. Getting yourself out the door is the hardest part.
If you live in MA, you probably have the right clothes. The hard part is figuring out the right combinations of clothes because you don't want to overdress. If you wear too much, you'll start sweating and then get really cold at stoplights. For me, I am dressed just right if I'm a little chilly during the first 1-2 miles. If I am warm from the start, I am probably dressed too much and will start sweating. I get around that by opening up zippers to let in cold air.