It's only you who can appreciate your own worth.
It's those situations when people turn their back on you, when you get to see their true colors. It's important to not start doubting yourself when that happens. It's not you, it's them. I know, it's hard to think like that when it happens, because it's almost like we're programmed to self-doubt ourselves, but it's true. You are still great and talented and creative and beautiful. It's them who for some bazaar reason can't (or don't want to) appreciate you any more. I used to get very upset when that happened. I would take breaks from doing things that I love, just to wallow in a cold bath of self-doubt. Just because one person decided that I'm not good enough. 
Age is a beautiful thing. Even now I can see a huge difference between me when I was 24, when this whole blogging thing picked up and now, when I'm 26. You just stop caring about these things and these people. And for me it gives an added bonus - determination. Even though there is no need to prove anything to anyone, only to yourself, it's a satisfying feeling to be proud of what you've done, when you've worked hard on it. 
If you ever feel like you're not good enough or you hear so many NO's that you could easily become a millionaire if you would get a dollar for every single no, never give up. Never. 21st century can be a b*tch in terms, when you see everyone being given these amazing opportunity's, working with amazing brands, having "the life", "the boyfriend", #goals etc. Especially when you can secretly follow those who are still "chosen", who are still on the list. Just put your phone away. Focus on yourself. Work on your content. You're just wasting your time and energy on negative feelings. Maybe I shouldn't be writing this either, haha and should do my makeup now for an upcoming post. I guess I've just had this all boiling in me on a low heat and there is something very freeing to get this out on a white screen.   
Also remember, when one door closes, another one opens. It's a fact.