It's okay to feel depressed. Be irritated; be sad; grieve the life you once lived and the life that you're not living now that you thought you'd be. There's nothing wrong with that; feel it all; get it out of your system.
But when you're through with that, let it go. Only look to the past for proof of what you can accomplish. Only look to the past to remind you of the power you're capable of. You have so many examples that you could use! Other than to bring you confidence or a smile, does it really serve you to go poking around in your memories?
You chose to do what you did because it felt right to you. Period. Don't blame the people in your life for being who they are and for doing what they do - it is who they are and what they do. Don't call yourself, or the choices you've made, wrong - because there are no mistakes and there is no "wrong." And it doesn't matter anymore, anyway.
Take the people in your life and your present circumstances out of the equation; put them out of your mind. Where do you want to go now? How do you want to spend your life now? Who do you want to be now? These are the only questions that matter. Answer them - and then stay focused on those answers. Define what you want. Imagine it. Don't keep looking at your present situation, being unhappy with it, taking score with where you are compared to where you've been or where you want to be. Keep focused on where you want to be - feeling gratitude for the good that already is, enjoying your blessings along the way - and then where you want to be (i.e. your shining best) will come to pass. There is no other possibility; the Universe is kind - but you can only see that if you trust that. Live in your dreams more; embody them; slip them on and wear them. Know your best life, the best possible version of yourself, so well, so intimately, that at any moment, no matter what's going on around you, you're able to close your eyes and experience your Joy so vividly that it takes your breath away. That is God. When you know that you can do that and that you have that, you know that you have everything - and that knowing is freedom.
The people outside yourself have shown you that they can't be relied on to take you where you want to go - nor should they be. They wouldn't even know where to begin. That leaves you.
You are your own best friend.
You are your own savior.
And that is the most liberating and wonderful news!
Can you feel it?