Greetings and peace be with you Desert;
Let's say a person was mentally tormented in life
I think you have two choices, you keep struggling through your life to come out on top; or you give in and let it beat you.
Belief is a powerful tool, whether you believe you can, or you believe you can't - you are probably right, it all starts from belief. If you believe you CAN beat your depression, then you keep pushing yourself harder, if you have a failure, you pick yourself up and try again. Failure only becomes a failure when you give in. When you suffer from depression everything seems like it takes so much effort, it seems like you have to run a marathon just to face your daily life.
The good news is that you can beat this, you can find the strength to keep going, you are not on your own, you can turn to Allah, and Allah wants what is good for all his creation - that includes you. Now you don't have to believe me, you first need to believe in yourself, that with Allah's help you can come through this. Allah will not put a burden on you that will be too heavy for you to carry; he is with you.
I don't think you ever stop struggling through life, you have some better times in between; somehow you have to get from your age to my age with a smile on your face, knowing it was all worth while. It can be done.
The alternative is to believe you can't can't beat your depression, so give up now, you have already lost and your beliefs were right.
May Allah bless you with the wisdom, strength, peace, perseverance and the resilience to do his will,
Eric