There is an old saying; "Suicide is a permanent solution to a temporary problem". But when you feel like life is unbearable, you lose awareness that your feelings will change. One of the most horrible things about being depressed, and many suicidal people are, is that there is a pervasive sense of hopelessness and despair that nothing you can imagine will relieve. Every thought you have takes you to a dark place, all roads lead to hell.
Whatever the reason is for planning a suicide, here is why it is a terrible idea: