I see others have said what I was going to say, which means it’s fabulous advice and you must therefore follow it immediately! 
I was going to say, stop focusing on the idea of getting the job, or rather, failing to get the job. It’s too high stakes, and paralysing with fear. Think about it as interview practice. Assume you’ll not get it this time and that’s absolutely fine. It’s not a failure because you’re not aiming for it.
What would you like to achieve instead? Set some new goals?
Maybe...
Go to the interview.
That would be ruddy amazing given how hard life’s been kicking you recently. It’s a Good Goal to set. Something to be proud of achieving. Really. I’m not just being kind, I mean it. Your self esteem is at rock bottom, you don’t have anyone in real life to support you right this moment. And you’re trying to do something that you really want but think is waaaaay beyond you, because you don’t think you deserve anything. So, although I don’t know you, I’m proud of you. I’m proud of you even thinking about going to this interview. I’m proud that you’ve still got that little spark inside that’s not letting you give up hope. That’s amazing and you need to give that little spark some space and some air because it can grow into a little bright flame... of life and hope and love and all that good stuff! One day you’re going to be a firework, but today, just concentrate on not letting that spark get squished by all the rubbish around you.
So.... let’s think about some little bit super important achievements. Each one is something to be proud of and should give you a bit of a boost as you do it.
Break down that bigger goal of getting into the interview, into all the little bits you can tick of as you do them. Each one is a great step forwards to get under your belt. Take them one by one, don’t look ahead.
Eg a few bites of light breakfast, sips of water, getting dressed up, more water, planning travel, travel to address. Finding the entrance. Walk through door. Smile at receptionist. Speak to her/him. Sit in waiting room. Nip to loo, take some deep breaths and some more sips of water. Smile and make eye contact with interviewer. Shake hands with interviewer. Say hello. Sit down in interview room. Answer first question.... if you do all that, you have achieved So Much.
You will have given yourself such a big step forwards, because you’ll have shown yourself you can do all that. And that means that next time, you’ll be confident and secure that you can do all that and you’ll be one step closer to the job you want in life.
Personally, I wouldn’t even think about the rest of the interview, but, if you are feeling super brave, you could give yourself another goal for in the interview itself? Like, answer 3 questions with confidence.
That’s it, just three, no more, don’t start thinking you have to be perfect and anything less than perfection is failure... because that’s how the voices in your head can beat you down and you end up not even noticing when you’ve done something good.
And that’s It. You CAN do this. And more than that, I think you need to do this, for yourself. Everything has been a drain on you recently, taking away self esteem, time, energy, everything from you, but this is about giving something back to yourself. Giving yourself some hope and faith, and some experience. Building interview skills which is something that is purely for you, which is a good thing, for now and for the future you.
