I had a series of epiphanies that really drove my success this time around (I've tried to lose weight for many, many years) - but I think one of the big things for me was truly embracing all the "failures" and actually learning from them. You can look at all your past attempts as failures that make you a failure - OR - you can look at them as opportunities to learn from, making you successful this time.
Sit down and make a list of what worked and what didn't work. Think of the times you were "most successful" - even if it was only a week. Was it a structured plan (Weight Watchers, Jenny Craig, Nutrisystem) or did you go it alone? Did you go to the gym and start walking in your neighborhood. Did you take classes at the gym, or do your own workouts? Did you have problems at specific times of day? Did you like and hate certain foods? Did you have support at home? With a friend? At a meeting (i.e., Overeaters Anon, WW)?
I think once you start seeing your patterns, it will be easier to move forward with something that works for you. I started slowly because my husband started running and wanted to get fit, so our eating changed. After I had dropped 10 lbs or so, just from eating
a little better, I bought the Zumba DVDs and did them at home. After dropping another 10 lbs, I joined WW online - another 10 lbs, I joined the gym. Now, I go to the gym 5-6 days a week, I take all kinds of classes (I am better with the structure of classes). I was having problems with motivating myself to lose the last 20, so I started going to WW meetings and I've already started losing again. So, what worked for me at the beginning doesn't work now - so I switched it up!
Be patient and know that this is a lifestyle change, not a quick fix. Try some things out, see what works for you and GO FOR IT! Today! Now! Future-you will thank present-day-you!