Some people have confronted the question of why they ought to continue living. This great confrontation can significantly divide our lives between before and after it into different experiences; it is a Pandora's Box.
I've found the existential view to be convincing: because existence precedes essence, reasons for living are fictions. I immediately clarify and stress that this is okay. The lack of true reason does not seem to prevent other forms of life from living, and we are odd because we demand such of ourselves. In Viktor Frankl's variant, it comes down to a meta-reason: we go on because we find meaning in doing so. That meaning is entirely relative to the one who lives. The point isn't that the reason be true; in order to be good enough, it must resonate within us, stir us to choose to go on.
With Frankl there is a pivot from philosophical reason to psychological outcome. When we face the great confrontation, it is resolved by the making of a choice. Our psyches define the parameters within which we make this choice. If the goal is to find the will to live then we can help ourselves by actively shaping our minds to promote that. What I'm saying is, we can teach ourselves to enjoy life.
This answer is simple, but simple ≠ easy. Speak only from my experience with depression: First I denied the answer, being glued to my prior views for my very good reasons. Then beliving in its possibility, for a long time its visceral truth was drowned out by pain and pessimism. I did not know how to hear my inner voice, and the lesson didn't take. Or I would find it for a period and then lose it.
The remaining ingredient, the answer to the difficulty, is practice. Continually, perhaps continuously, sustain the knowledge through ongoing effort. Make finding your meaning, holding your meaning, and amplifying your meaning into your way of life. Make the living of your life an act and art of self-expression. Like all habits, eventually it will stick and not be an effort, and like all learnings, eventually it will work its way into your system and bear fruit.
I mean all these things with this motto, which is my personal answer to depression:
Make life worth living.
The "making" is an active verb. It is a choice to find meaning, and to create its truth for ourselves through our curation of our minds by habitual practice of self-expression.
A final comment. It may be hard to distinguish what I'm saying from "Just make yourself happy and keep trying." Maybe there is no true distinction, only the meaning you find in the directive. I'm aware and I don't callously expect to have changed your mind. Rather, I'm laying my cards on the table and inviting you to see for yourself.