To dovetail on what blueduck has said, take it one day at a time. I was very very heavy and through changing my eating and exercise habits, I went from a size 26 to a size 16. Not skinny, I know, but I'm a much more manageable size, and I have incredible energy.
Now back to you! (smile) You may want to start slowly by cutting out Sugar
and white flour, increasing your water intake and increasing the amount of raw fruits and vegetables you eat. Yes, keep reading. I became a raw foodist after reading so much about dairy and the meat industry. To keep myself sane, on day per month I eat what I want. Believe me, I regret it the following day - but like I said, it keeps me sane.
Keep a food journal. Keep track of what you eat, the amount of exercise you do (20 minutes per day is a great start! You can walk, jumprobe, TaeBo, dance, clean vigorously - ANYTHING to move your body and build up a good sweat. I'll tell you what else helped me. I bought a book called "10 Days to Self Esteem." I worked through it - and it helped me to build myself up from the inside out.
I am a totally different person. I'm happier, friendlier, more energetic. And I did it for ME. If you are eating bad foods frequently, don't set yourself up for possible failure by saying "I'm not going to eat anything but lemonade until I lose this weight." For ME being so heavy, that would not have been a realistic goal. Making changes in moderation, taking it one day at a time, remembering the big picture and reinforcing my good acts with positive messages to myself helped me be successful.
If you have more questions, you can email me at email@example.com I'd be happy to share my experiences with you. And if you're not interested and want to do it your way, that's cool too! I wasn't trying to be a "buttinski." I wish you all the luck in the world!