I feel so I have to respond to this From a literalist point of view, to ascertain if a sin is damnable and unforgivable or not we must see what the Bible literally says.
Matthew 12:32 New International Version – UK (NIVUK)
32 Anyone who speaks a word against the Son of Man will be forgiven, but anyone who speaks against the Holy Spirit will not be forgiven, either in this age or in the age to come.
This is the only verse in the Bible that says something can not be forgiven. Suicide does not constitute blasphemy against the Holy Spirit.
Matthew 5:28 New International Version – UK (NIVUK)
28 But I tell you that anyone who looks at a woman lustfully has already committed adultery with her in his heart.
Exodus 20:17 New International Version – UK (NIVUK)
17 ‘You shall not covet your neighbour’s house. You shall not covet your neighbour’s wife, or his male or female servant, his ox or donkey, or anything that belongs to your neighbour
In other words “Don’t even think about it!”
Now obviously someone who has tried to commit suicide has thought about it. A lot more people who have not tried to have thought about it also, are they now eternally damned? Certainly not!
Furthermore, any suicide or attempted suicide is a cry for help.One of the people they cry out to help to is the Lord.
Romans 10:13 New International Version – UK (NIVUK)
13 for, ‘Everyone who calls on the name of the Lord will be saved.’
A Pilgrims Ramblings 