In order to stay motivated, you have to be motivated by something. Motivation is what keeps you motivated. Oh, this is so confusing! Let's simple it up a bit.
Set little goals. Goals like, running a 1/4 mile. Then, run your little 1/4 mile. Done! Motivated to run more, now 1/2 mile. Done. Motivated. Run. Oh, it's insanity. Fuck yeah, it is because you are motivated. How do you stay lazy? Easy, just don't anything! Well, it works the same with staying motivated. Do something. Set goals. Meet goals. Break goals! Make more goals. Meet goals. Motivate yourself to stay motivated.
How do I stay Motivated? Only you can answer that question. How do you stay motivated? What keeps you waking up after you sleep? What keeps you looking at your phone when it goes off or when it doesn't? We all do it! What keeps you eating when you are hungry. What keeps you smiling when you're happy? Define these things! Think them out in as much detail as possible. What are the reasons?
What keeps me waking up is that I have yet to complete the things I have set out to complete. I look at my phone because I want to be there when someone needs me. I eat because well I love food. Ha ha! I smile not because I am happy but because it makes you happy, in turn, makes me smile! That's motivation. That's how you stay motivated! Stay alert! Stay available.