I've read so often that God is more interested in our character than in our giftings. How can a person build character and become a better person?
I'm particularly challenged by this personally as I am forty three and haven't worked for some time due to mental illness - I don't want to focus on the illness but it has led to a downward negative spiral.
Suffering ultimately builds character. "Work" is inside, like pain, a factor of the mind/heart.
You can not judge yourself. People are too complex and get too little information to do that. Though you should be able to ascertain whether you have done good or bad, so as to have assurance of salvation.
"Mental illness" is a modern term. It largely relates to psychosomatic disorders and if you believe you have incapabilities which are incurable in the mind, then you have little recourse for escape until you change your way of thinking. These are actually even more susceptible disorders then somatic/body ones because they may not even have any physical manifestation at all and can be entirely in your mind.
Even bodily disorders are influenced in this way by thinking, therefore people can be healed by belief. If you believe people can be healed, truly, you can pray and have them healed.
This does require faith and where there is no faith such things can not happen.
The gospels are real, all those things really happened.
The devil is ferocious today, last stand stuff, and I believe there is a beast system which supports the devil that forces everything and anyone to operate by the so-called principles of the material world.
Metaphorically, that is Babylon which people have to get out of.