Before anyone dismisses me as a troll for questioning this person, I will give my best answer...(It may not be what you expect, though)
Many many months ago, when I was still a newb in CC, I once stated that suicide is a sin because if it isn't, well, I expect many more Christians to commit suicide immediately after being saved or at least quite soon afterwards because technically they will get to enjoy their happy eternity in heaven sooner than if they decided to stay behind. But...there are more than a billion LIVING Christians out and about as of now, so clearly they know something that takes the option for immediate suicide out of consideration for at least the majority of people. I'M NOT SAYING THAT YOU WILL IMMEDIATELY GO TO HELL IF YOU COMMIT SUICIDE, but it's better not to risk the unknown in this case. So please don't do it.