Why can't I just do it?

Motivation is a fickle beast. It's what gets you started and gets you excited, but you can't rely on it to stick around. You have to learn to commit and be consistent even when you don't feel remotely motivated.

The only way I have been able to be successful is by making small changes that I can live with, and keeping doing them until they are proper habits. The thing is, you only really need a calorie deficit to lose weight. Good nutrition and exercise are wonderful things, and to be highly recommended, but they are not necessary just to lose weight. So, I'm not suggesting you don't care about those things, but in the beginning, keep it simple. Use MFP to set a reasonable calorie deficit (ie big enough that you're losing weight, not so big you feel like you're on a starvation diet) and just go from there. Eat the foods you like to eat. Track it. Continue.

It's not about "healthy foods" and "bad foods". It's about having an overall diet that supports your health and having a healthy weight. You don't have to start cutting out all the foods you really enjoy eating, and calling them "bad". First, eat to meet your calorie goal. When you have that sorted, start looking at your overall diet and make sure you're getting enough protein, fat, fibre, vitamins and minerals etc. Look at what foods you could do with adding, rather than being super restrictive.

As for exercise, if you can add some in, then great. It has tons of benefits, one of which is helping with those feelings of depression. Don't force yourself to do hours of something you really hate though. Find something you like doing, and if you start off with something gentle and low-impact, that's absolutely fine. The calorie deficit will come from your diet. Getting regular exercise is wonderful for your overall health, and making it a regular thing is far more important than burning hundreds of calories per workout.

I think people find it hard to get started, because it seems like this insurmountable task, especially if you have quite a bit to lose. People look at it as a period of self-deprivation they have to go through, a kind of trial by fire, something hard but temporary that they will do to get the weight off and then they can go back to normal. That's not how it works. This is going to take a long time - a really long time. It will never really be over if you intend to maintain the weight lost, so you need to look at making changes that you can actually live with. It's a long road, and it's not always easy (otherwise everyone would be slim), but it doesn't have to be torture either. So, don't "go on a diet"' keep things simple. Hit your calorie goal.

Check this out too: http://www.myfitnesspal.com/topics/show/1080242-a-guide-to-get-you-started-on-your-path-to-sexypants

All of the above, unless you are clinically depressed, in which case you might benefit from a visit to your doc, or therapy, or a combination thereof? I know when I am depressed it feels almost impossible to work on any goals (career, home, self-care, etc.). This time of the year is bad for those of us who battle depression. Good luck to you!

Because you're eating food you don't like and doing exercises you don't enjoy, probably.

No one wants to do and eat stuff they hate for the rest of their lives.

I always tell myself that this next month, year, whatever, is going to happen whether or not I eat right. I can either waste the time and feel just as depressed later or I can push through the tough days. Then, when that next month has passed and I've done well, it's easier to look at the next month and say, "welp, this next month is going to happen with or without me, what am I going to do with my time?" Good luck, lady, it gets easier as you go, I promise!

Do you hear a voice inside your head, telling you that you are a failure, that you should quit, give it up, you will never be good enough, pretty enough, that you deserve to be sad, unhealthy and overweight, that good things are just out of your reach...

We all do. This voice, in my humble opinion, has always guided humanity, always spoken to us. It is neither good or bad or an angel or a demon. It means only to protect us, no matter the costs, short term or long term. It evokes our fight or flight mechanism. It's a drill sergeant, a tough coach who drives us to do the impossible.

Over the course of human history, this voice has protected us from failure by backing us down and pushed us over the limits of what we thought possible. But all we hear in the modern world, all we think we hear is that we should give up and that's what we do, because the known feels better than the dark, b/c it's easy to take the path that is clear and well-traveled.

Listen to your voice carefully, listen to it with an open heart, open your mind to it's wisdom. It will push you forward, beyond the impasse, around the bend, if you let it or it will push you back, for your protection b/c you are not ready for the journey. This voice always thinks about 5 minutes out, there in, lies it's weakness, it will make you give up the long-term gain for short-term pleasure b/c it wants to protect you no matter what.

You have to decide how you want to listen to the voice, you have to make the decision, will your step forward toward the long-term or will you step backward until you know you are ready. Know this, you have the capacity for great things, you can overcome just about any obstacle, you just have to be ready and commit.

I hope this helps.