This is a quotation from Pilgrim's Progress Part I, Section IV:
"HOPE. Indeed our present condition is dreadful, and death would be far more welcome to me than thus for ever to abide; but yet, let us consider, the Lord of the country to which we are going hath said, "Thou shalt do no murder," no, not to another man's person; much more, then, are we forbidden to take his counsel to kill ourselves. Besides, he that kills another, can but commit murder upon his body; but for one to kill himself, is to kill body and soul at once. And moreover, my brother, thou talkest of ease in the grave; but hast thou forgotten the hell whither for certain the murderers go? for "no murderer hath eternal life," etc."
Saul killed himself and he went to heaven. Sampson killed himself and he went to heaven. If you can lose your salvation for killing yourself, you can lose your salvation for committing any sin. "For whosoever shall keep the whole law, and yet offend in one [point], he is guilty of all (James 2:10)." John Bunyan is another example of someone trusting themself for salvation, and not trusting Jesus Christ.
"HOPE. Indeed our present condition is dreadful, and death would be far more welcome to me than thus for ever to abide; but yet, let us consider, the Lord of the country to which we are going hath said, "Thou shalt do no murder," no, not to another man's person; much more, then, are we forbidden to take his counsel to kill ourselves. Besides, he that kills another, can but commit murder upon his body; but for one to kill himself, is to kill body and soul at once. And moreover, my brother, thou talkest of ease in the grave; but hast thou forgotten the hell whither for certain the murderers go? for "no murderer hath eternal life," etc."
Saul killed himself and he went to heaven. Sampson killed himself and he went to heaven. If you can lose your salvation for killing yourself, you can lose your salvation for committing any sin. "For whosoever shall keep the whole law, and yet offend in one [point], he is guilty of all (James 2:10)." John Bunyan is another example of someone trusting themself for salvation, and not trusting Jesus Christ.

