The Father KNOWS our heart. Suicide is not unforgivable as a sin. What IS unforgivable is knowing the Truth, accepting Salvation, then denying Christ when you are asked to Witness. In the Bible, that is the only unforgivable sin I have read of.
Peter, who correctly identified Jesus Christ as the Son of God denied Christ three successive times after Jesus was arrested. Jesus certainly forgave him when He appeared to Peter after He arose.
Christians unfortunately and too often live and behave in ways that deny Christ by their words and actions. Forgiveness is extended to them as they request it of Christ, because "He is faithful and just to forgive us our sins." (1 John 1:9). It is His promise to us.
The unforgivable sin of denying Christ is applicable to the one who refuses Christ as Savior.
FReegards!