Fisrt of all, you should know that that's ok to feel demotivated sometimes, especially when we live in capitalism, that makes us think about the survival. We need to think what to eat, what to pay bills with, where to live and so on.
And whatever you've decided to do, you should always have the "why" answer. If you don't have any, or if the one you have is superficial, if it doesn't go deep, if it doesn't suit your truly needs, you will always feel demotavatied. In that case you should probably just find another thing to do, that will make you happy even in such dark moments.
And you should also know about the imposter complex. The modern pshycology, finally, admotted it as a problem.
The imposter complex makes you feel not worthy of anything: love, money, fame, friendship. It's like someone is saying that that's just a coincedence you've reached something, you don't truly deserve what you have, and you won't reach anything anymore. The sad thing is that the modern psycology doesn't tell how to overcome this.
And to overcome this you sould understand that all these thoughts are an evolutionary mechanism that used to help you to survive. It once was a really useful mechanism, and without it, the human kind woulnd't come so far and we wouldn't be who we are
But it's not actual anymore, and you can be free just not to listen to these thoughts. Just remind yourself that all these "demotivating ides and emotions" are not yours. They used to be, and they ised to be useful, but not anymore.
So, remember 2 things:
1. The answer "why:
2. The imposter complex that make you feel not deserving something )