How To Stay Motivated Forever
Simple answer: You can’t.
Motivation is an Emotion, and Emotions never last, nor are they consistent in any way.
But, there is always something you can do to affect them.
For instance, while you may not be able to will yourself to feel happy, the chances that you feel happy when you listen to happy songs or are watching comedy movies.
Similarly, if you only listen to songs with sad lyrics, watch Dramas and never stand up or go outside, chances are higher you will not feel so good.
In this way, you can also increase your chances at feeling motivated, although you will not necessarily be able to create the emotion.
The best way to bring forth any emotion is to understand your own triggers and set those up everywhere.
They are fleeting, and will come and go as they please, but that also makes them that much easier to fleetingly obtain.
If you change your desk layout to remind you of your life dreams, add motivating backdrops to all devices, and wear clothes that remind you of success, you will be more likely to feel what you want to feel.
One of the tricks used by many successful people is to tie a certain reminder to an object you carry with you.