Alright. My first answer was facetious but upon further reflection...I just finished tonight's ride home
...I do have some suggestions. I've been cyclocommuting continuously since 1981 and haven't missed at least one ride per month since then, including a broken ankle and surgery to remove old hardware in 2001, so I know a little about motivation
1. Set goals. I hate setting goals (I'm prefer letting life happen and being surprised) but they help. In 2001, I hit my lowest number of commuting days, around 80, ever. I was spending too much time on airplanes and working way to many hours. The next year I decided that I was going to ride 3/4 of the work year -195 - and I set out to do it. I failed.
1a. Set realistic goals. When you look at a whole year ahead of you doing 195 days is a daunting task. Think of it like you would a long journey or if you wanted to do a century. 100 miles is a long ways but is 10 miles? 10 miles is easy. A century is just ten 10 mile rides. Break the year up into months and to meet those minigoals. I have records going back to 1988 and I know how many days I've ridden to work since then. This year I set a goal to ride more in each month then I had ever before. I've failed.
1b. Don't be afraid to let your goals slip a little. If you fail to meet one, it okay. It gives you something to shoot for next year. This year I'll be at around 170 days. Next year all I have to do is ride 2 more days per month to reach 195 days. It's not that hard.
1c. Leave something for next year. Come on, if you meet or exceed your goal, what's next? And don't try to make too many goals. One pre year is enough!
2. Find something that you want to do on a bike and use bike commuting to get to that goal. In 2003, I decided that I was going to do a trip on the Lewis and Clark Trail. I needed to be in good shape for 3 weeks and 1000 miles of riding and carrying my own gear (I did the trip solo and unsupported). So I started riding early in the spring with an eye on a Memorial Day start. I had to delay it to Labor Day but I hucked 40 lbs of bean and rice in panniers back and forth to work for the whole summer. I did the same in 2005.
3. See how little you can use your car. I was somewhat serious about looking at your gasoline bill. What you don't spend on gas, you can spend on your bike!
Now get out there and ride!