Life is the most precious gift to man from God. God granted this gift in the creation. He reestablished this gift again in Christ Jesus (John 11:25). Throughout the Bible, God has stated His feelings about the sanctity of life. "Surely for your lifeblood I will demand a reckoning; from the hand of every beast I will require it, and from the hand of man. From the hand of every man's brother I will require the life of man. Whoever sheds man's blood, by man his blood shall be shed; for in the image of God He made man" (Gen. 9:5-6).
If one were to read the pages of the Old Testament, they would find that the Law commanded "life for life" (Ex. 21:23). Life was not to be taken, unless it was commanded specifically by God for His higher purpose (1 Sam. 15:3).
Jesus fulfilled the Law by commenting on God's purpose for mankind in the coming Christian age. He discussed not only sinful actions, but the thoughts and motives behind such actions. It was not just murder that was condemned, but hateful thoughts and emotions (Matt. 5:21-22). When people begin to hate themselves, they are missing God's intent for their life and rejecting His genuine and abiding love. There are certainly situations where suicide would lead to eternal death. But only the mind of God has the power to save or damn the soul.
I believe there are cases where those who commit suicide could find forgiveness. I understand from Jam. 4:17 that accountability and knowledge are intertwined. Those who have their mental and emotional faculties in check are obligated to do things that are in harmony with God's word. If we can distinguish between good and evil we are subject to the consequences of whatever path we choose. (I am not speaking with regard to "crimes of passion", rather I am stating that situations exist where the capacity to reason may be absent).
The mind is a very delicate and fascinating organ. What is in the mind of others can only be known when it has been revealed (1 Cor. 2:11). What we know from the mind of God has come through His revelation (1 Cor. 2:12-16), and these things can only be discerned spiritually.
I am not in the place of God, but I have personally known individuals who have committed suicide who were severely challenged by mental illness. No doctor, medicine, or counselor was able to dissolve the problem. I had a good friend. He was a mentor, a Christian man, a preacher, a teacher. He was not perfect. He sinned daily, as I also sin. But the blood of Christ was available to cleanse Him as he repented (1 Jn. 1:9). He was diagnosed as bi-polar, and there were other issues. He struggled mightily for years with the notion of ending his life. He knew what the will of God was on this matter. His fight to overcome for years helped so many others. But, in the end, he took his own life.
I fully trust in the Giver of life to give life again. Just as sure as every knee shall bow and every tongue shall confess to God that Jesus Christ is Lord, so God will judge in righteousness. On some mercy, and upon others, justified wrath. Either way, "Shall not the Judge of all the earth do right?" (Gen. 18:25).
There may be some cases where suicide seems to be a very clear and open disrespect for life, our richest blessing. In these cases God's wrath will come upon those who reject not only life, but the Way, the Truth, and the Life (Jn. 14:6).
But as each soul is different, so are the events that determine the direction of the soul. I believe that some have ended their lives unwittingly. I pray that the grace of God will rest upon them.
In the meantime, the Bible teaches that we should have great respect and love for life. It is a gift so precious that the Son of God left heaven to provide for it eternally.
We must also resolve in our minds that we don't have to answer every difficult question. Biblical faith is not having all the answers, it is trusting in the One who will reveal the answers in His time.
"If You, O Lord, should mark inquities, O Lord, who could stand? But there is forgivenss with You, that You may be feared. I wait for the Lord, my souls waits, and in His word I do hope" (Ps. 130:3-5).