By committing suicide you may walk away from your problems hence problems aren't solved and you carry them with you to a temporary afterlife and/or immediately in the next incarnation. Your taking of life will lead to suffering and pain in others, pain that you will most likely have to heal again in the afterlife and/or the next incarnation. I realize there may be exceptions, like if you lost everyone. It is also trauma/shock and violence towards yourself, which as well requires healing. The person may be in great suffering/pain but the consequences to others should not be underestimated.. you can't walk away from responsibilities, sooner or later it comes back.
I know it may suck to hear this but I think responsibility and facing one's problems are essential to spiritual growth..