Remember this point, when a person commits suicide they most deeply hurt the people that love them the most. Is that right? Is that fair? They don't hurt the people that don't care about them, they hurt the ones that love them. It's such a cruel, unjust thing to do.
Everyone dies eventually. Having a loved one kill themselves vs any other reason, you can never really get over it. It's just a punishment to the ones that love you that continues on. So we are left with two reasonable options. First that you do it out of spite and anger to intentionally hurt people that love you. Don't need to talk about that, that's just wrong. Second, you think no one loves you.
So that last case, if really no one does love you, it's still not noble. It is the ultimate quitting, the ultimate admission of defeat. And it is irreversible. You feel this way now, at this moment, but you give up the chance to feel another way ever, for any redemption.
A wise person once told me that arrogance/selfishness and depression were two sides of the same coin; an unnatural focus on self. Life is not worth living? Fine. Die to yourself. Stop thinking about yourself. Your life sucks, its going to suck, fine. Start thinking about other people. You are walking dead already, but you still have a brain and some abilities. Do something for someone else.
Another extremely wise teacher, who tried to convince people to love each other, said this: "If any of you wants to be my follower, you must give up your own way, take up your cross, and follow me." meaning before you could be like him and live for others first you need to die to yourself. And then he said that those people would find true life.
Edit: I'm not just saying this and telling suicidal people to suck it up. I've been through this personally from all these angles. I'm sharing what I have experienced and what worked for me.