Historically I would have to say most people don’t stick with their New Year’s resolutions but why? When it comes to weight-loss… you did not gain the weight overnight so when you resolve to take it off by the bikini season… is that realistic?
The folks at diet.com did a nice narrative about the top five reasons your diet won’t work. The list includes, (5) starvation diets, (4) eating junk food and sweets, (3) not doing strength training, (2) not varying cardio exercise, and (1) eating too many calories. Watch this video to see their perspective (which I generally agree with by the way).
I will quickly address each point. If a person starves themselves to lose weight (assuming weight loss is the goal instead of fat loss), this will work great for a while! But. It is not good to lose weight when it is muscle!!! A person should try to lose fat - not muscle. Fat can be burned from aerobic exercises and by moderately dieting. If a person eats too few calories, it exceeds the amount of fat the body is able to burn and then starts breaking down muscle! You will lose weight fast but also lose the ability to burn fat as fast. Muscle is the only thing that can convert fat to energy, so less muscle, slower burning of fat.
Junk food and sweets are very high calories. I don't think one has to avoid all junk food but try to keep it to reasonable levels... otherwise you are just defeating the fat loss goal.
Strength training can add muscle, and thereby burn fat faster, and thereby lose fat faster than moderate dieting and cardio exercise alone.
The body gets efficient if you only do one kind of exercise. That means that you should change up exercise and levels (such as go hard one day and moderate another). If you change up routines, you body will not fall into a plateu as easy and you will achieve your goal.
Like it or not, most of us that do not count calories will end up eating move then we think! If you are serious about losing fat - keep this advice in mind when you are designing something that will work for you... no one has all of the answers but with diligence - you can and will succeed with your goals!

I greatly appreciate your optimistic views! “I think I can, I think I can …!” Thank you!