Welcome to the forum.
Five years is a long time to live with depression although it can become a chronic condition. Why do some get well quickly and others not is a good question. I put it down to our differences in health and resilience. We have many things in common but we are all individuals with our own traits.
There is this huge debate about nature vs nurture in the way we are shaped and I think this is where we learn how to manage our lives. Struggling with motivation may have become your default coping mechanism because you did not learn to manage any other way. Well I will leave that to the professionals and say you are not alone. If being motivated in all, or at least most things, was easy we would have no problems.
Being overwhelmed has been my problem at different times and I was discussing this with my doctor a week ago. She tells me that while I still get overwhelmed at times, and this is normal, it lasts for much shorter periods, is not as intense and I can usually make an automatic response in coping. It has taken a while to do this.
You have not said if you are taking any medication or if you are receiving help from a mental health professional. There is no obligation to tell us, I mention it because I want to offer suggestions that you have not tried before. I invariably suggest a person has a long chat to their GP as the first step. It can be the start of a journey to healing and health.
It's good to get a general health check as well as discuss this motivation difficulty. I suggest you complete the Anxiety and Depression K10 checklist. Look under The Facts at the top of the page. This is not a diagnostic tool. It gives an indication of where you may be on the mental health scale and a starting point for discussion with the doctor. Even if you already have meds it's a good idea to have a periodic review.
I found several ways of managing. Divide the task into small parts and tackle each one separately without referring to other parts until the previous task is done. That was the easiest but not always successful. Time constraints had an effect also.
I can now sit and look at the problem, albeit with some anxiety, and work out why it appears to belong in the too hard basket. Why am I afraid or reluctant to get on with it. I had lots of help from my GP and psychiatrist who was helping me manage my depression. Maybe you would benefit from seeing a psychologist a few times to work out a plan to cope. Ask your GP about this.