Being motivated is hard work, staying motivated is harder, trying to motivate yourself is like trying to drop a glass from a 3-story building and it not breaking.
Needless to say, motivation is what pushes us to do things. Our bodies send us signals to motivate us to eat and sleep, our brain releases chemicals to promote one activity over the other. But what if you have to do something that the rest of you is saying "no thanks" to? This is where self-motivation comes in. If you truly, 100%, don't want to do something, no self-help book in the world can help you. You first must be willing to at least try.
This first step is the most essential; and the hardest. Understanding the reason why you want to do something is something everyone struggles with. I can get super pumped about something for a little bit only to have the excitement and newness fizzle into a bleak, uninteresting past. From exercise to education to entertainment, finding the motivation to follow through with a goal takes many, many failures. The key to motivating yourself is to figure out why. This is hard because it takes introspection and many harsh truths. Why do you want to loose weight? Why do you want to exercise? Why do you want to be friends? Why do you want anything? Some may genuinely want to loose weight to better their health, others may want to loose weight to look better or be a different size. Finding out what motivates you is what pushes you further. I am in no way saying all motivations are good. Many health professionals, for example, would say that loosing weight to look a certain way or be a certain size is a recipe for disaster. I would agree, but understanding your motivation can create motivation for not doing something as much as for doing it.
Once you've got the why down (and this can take a few years, but don't give up, it's worth it!), you can start focusing on the how. How will you accomplish your goals? How will you motivate yourself to do things even if you don't really want to? The trick here is finding what you do want to do and do it in a way that accomplishes what you don't want to do. Sound confusing? It's actually quite simple. Let's go back to exercise for a second. I for one am not a fan of exercise. I am, however, a huge fan of hiking and rock climbing. But Amanda, you say, those things you like to do totally count as exercise. Why thank you! Yes they do, but I don't see them like I see going to the gym and lifting weights or running because I enjoy doing them. And that enjoyment makes all the difference. When I do things I like, those little chemicals in my brain say that I'm not exercising, I'm having fun! Not everything has to be so conventional that you can't find something you like doing. Don't like reading? Try podcasts or audiobooks. Can't finish a TV series? Try a movie or shorts. Hate eating that salad? I'm about to blow your mind... there are other vegetables besides salad. Experiment with yourself and try new things. You may be surprised by what brings you joy and happiness.
One of the places many people have issues with motivation is their jobs. No one likes to "work". Everyone will tell you that you should find a job that you wake up every day looking forward to. Not to burst your bubble, but there is no such things. No job is perfect. Even people that love their jobs don't always wake up excited to go to them. No, the best way to stay motivated on the job is to understand why you are doing said job, what benefits that job gives you and others, and how you can make your job more fun for yourself. If you have a retail job, try finding way to amuse yourself. I often pretended I was acting in a movie or something, especially when rude customers decided they had a bone to pick with me. It made it easier to get through. I also liked being able to have a coupon to basically everything in the store and that I got to see all the new merchandise before it went out. If you have an office job, try making your office/cubicle more personalized. Fill it with things that make you happy! I have a standing desk that has improved my life so much it's crazy. No matter what kind of job you have, finding what makes it worth it (beside that sweet, sweet promise of money at the end of the tunnel) can make it infinitely better.
If you're having a good time you don't focus on the end goal, you enjoy the process. This is the true secret to self-motivation. You can do things one way and be miserable and still get results, but chances are you won't be living a very fulfilling life and you probably will eventually stop because, I mean, it sucks to hate what you're doing. On the other hand, you can try new ways to accomplish the same goal until you do something one day and realize you actually enjoyed doing it. Self-motivation is not a step-by-step process. The path from the why to the how is different for each and every person and not every person finds it. It requires you to really dig deep, understand yourself, and be willing to try. Good luck!