Firstly, and perhaps most importantly, you're not alone. I'm not sure if my story will be helpful, but perhaps you can draw something from it.
It's been about 4 years since the start of my decline that included me terminating a marriage which wasn't even the bottom of the hole, that was about half way down the descent. Up until that point everyone around me looked at me as successful. Some days they look at me still and classify me as successful, and to some extent I guess they're right. I have what most would deem an impressive job, good income, two amazing kids. But what people see isn't the reality in my head. Of course, I know the reality in my head is just the depression talking, it's not real, but it feels real and that makes it real, to me.
For me, I found Quora a huge help. Answering questions - specifically those that made me really deeply analyze my own mental state, my relationships, what I really value in the world, who I am, how I got here, what I'm thinking, why I think what I do. The act of self analysis and writing about it in a manner that I thought would be helpful to other people was probably the best therapist I could have asked for. Just talking about it is huge! I started off with the questions I felt were easy to answer, sort of an ice breaker and gradually worked up to the hard "face your own existence" type questions.
This process may be helpful for you, it may not. Perhaps a real skin and bones therapist would help. The apathy and lethargy of burnout aren't just a figment of your own imagination, they're your brain's subconscious way of telling you that you need to stop. It's telling you it needs to rest. It's telling me to stop taking care of everyone else's shit and take care of me for once.
As for "getting back," I don't think that's ever going to happen for me. I'm not the same person I was when I started this journey. There is no getting back, nor do I want to. I've realized and remembered a lot of things about myself and my core values that I had let get bulldozed aside by things that don't really matter to me.
On Sunday everything I spent the last 4 years learning about myself was solidified in an instant when at 6:15am I was awoken by a massive explosion across the field from my bedroom window that wiped a house completely off the map, evacuated 35 people from their homes, including someone I care very deeply about who lives 2 doors from the explosion, and left a man dead.
I will never be going back to letting other people's needs and priorities usurp my own. The fact is, work doesn't make me happy, money doesn't make me happy. It's a means to an end. At some point, I'd made work my priority and let myself believe it was more important than me. I'd let myself believe it made me happy. It doesn't. Problem solving is my compulsion and something I'm really good at. Work enables and feeds that compulsion. That compulsion feeds my family and puts a roof over their heads, but that compulsion doesn't make me happy, it's just a habit like biting my nails.
I want to do something that matters, to me. I'm inspired to do things, I'm full of excitement and wonder again like I was before, I feel joy. But I'm not inspired by stuff that doesn't mean anything.
It may be a while before you figure out what it is that matters to you. You're grieving. Well not really grieving, but the process is similar and can't be rushed. You can't reason with emotion, you can't feel good just because you tell your brain to feel good. You can't rationalize your way out of it. It's a process that you kind of have to go through.