That is a huge question, and I don't know the answer to it.
I have been severely depressed since I was a young child, and it deepened as a teenager and an emerging adult and then solidified even more when I was an adult. I would like to think one day I would not live with depression, but I don't know if that is my path, now I don't focus on that I focus on working on myself. Getting on top of the distorted cognitions - that is thoughts, feelings, perceptions and ideas - is a big focus in my life today. I have a continuing thread on that in social.
I have gone from the highest severest suicidal depression on the Burns scale down to having moderate depression, now I am aiming for mild depression. It has taken a lot of work, but it is really worth it.
It is not easy, but 1 minute per day is all you need to do. per day to start.
I would suggest the book, that I am so grateful that Anthony suggested, David Burns' book "Feeling Good: The New Mood Therapy. The Clinically Proven Drug Free Treatment for Depression". I didn't know that so much of my experience was depression before I read this book. I thought it was just me.
I have both the book, audiobook and CD of the "The Mindful Way Through Depression: Freeing Yourself from Chronic Unhappiness" by Mark Williams, Jon Kabat-Zinn, John Teasdale and Zindel Seagal. And that does explain depression really, really well. It is possible to to change and heal, I think it is about finding what works for you and then doing it to create new neural pathways in your brain.
As well as challenging distorted cognitions - on a regular daily basis, doing Mindfulness for an hour, I also exercise at least two hours per day. I do things for my communities. I support other people in their recoveries. I run challenges on this forum. I do random acts of kindness. I also practice gratitude. I also spend time in nature and I go to therapy as well with a psychiatrist who is very good with psychotherapy with a keen interest in PTSD and Complex Trauma. Currently I am learning about and starting to practice self compassion. There are many avenues that you can explore to recover from depression.