why do I feel so down when everything is going well for me?

To motivate yourself you can chart out short term targets and follow them. Give your best and things will look better.

Sometimes even when life is okay or even great, people with depression feel down, perhaps look into this?

In my eyes, if you are happy for a long period, the brain looks at other parts of your life that makes you upset. These feelings are very hard to deal with, especially when things are well and you aren't happy with the things that should make you happy. The important part is to remind yourself that you are happy and you will keep being happy.

There may be a issue you just don't feel but that doesn't mean it doesn't exist. You could try to analyze your feelings or ask a professional to do that for you

You may be focussed on the things you are yet to improve but want to change. It is important to recognise where you can improve your life to ultimately become happier, but we must counterbalance this with the things that are in fact working for us (i.e. we are employed, in school, have friends, have a nice home). Part of being prospective and looking over the horizon to what could be next in our life involves being retrospective. We must turn around and observe the path we have navigated to get here. Change can be very slow and because of this slow pace it isn't until much time has passed and we may feel not much has changed that we can then turn around and really appreciate how far we have come. To be prospective you must simultaneously be retrospective. You can still travel of mile with baby steps.

sometimes i start stressing about the future a lot. I think i have it all figured out in the moment but i dont know what the future holds and that scares me a lot. I think i feel so down because i am faking how happy i am in the moment. It feels as if inside my head everything is falling apart and on the outside no one is able to tell this. I get one moment of happiness that gets taken from me when snap back into reality most of the time. This usually hits me at night.