There are a couple issues here.
Strictly speaking in a logical sense this is the best thing a person could do for themself.
No. Suicide is never a logical solution to any situation. If anyone is in a position where they think it is, they would be best served by taking a time out and then seeking help.
But this question is not really about suicide.
- Perhaps the greatest thing a person can hope for is to enter the Kingdom of Heaven.
- We are told that if a person truly accepts God as their Saviour, they promised an eternity in heaven.
With this in mind, why not just accept Christ and then off ourself? We all want to go to heaven don't we?
The biggest problem with this logic is its premise, the characterization of Christianity as nothing more than accept Christ as your savior so you can go to heaven.
Nowhere in the New Testament does it say it is enough to "just accept Christ". Rather, when Jesus called his disciples, he told them to follow him. In the case of four fishermen (see Matthew 4:18-22) this meant leaving behind their boats and nets, their entire way of life, and even their families. Following Jesus meant abandoning everything that came before and starting a whole new way of life.
Jesus alludes to this in Luke 14:27-28.
Whoever does not carry the cross and follow me cannot be my disciple. For which of you, intending to build a tower, does not first sit down and estimate the cost, to see whether he has enough to complete it?
There is a cost to following Christ, and the cost is abandoning our own willfulness and sinfulness. We must give up everything that stands in the way of following him.
For a wealthy tax collector named Zacchaeus, it meant paying back those whom he had cheated. For another rich man, the cost was too high. For the apostle Paul, it meant giving up his claims to righteousness, and indeed, everything that had been his identity.
The point is, once we make the decision to, as they say, "accept Christ", our life is no longer our own. It's all about what God wants for us, and not about what we want.
Jesus expresses this as a paradox in Matthew 10:39.
Those who find their life will lose it, and those who lose their life for my sake will find it.
He's not talking (here) about literally losing our lives. He's not asking us to "off ourselves". He's talking about changing our very identity. This is known as sanctification.
Our human nature is sinful, bent to our own desires, but when God sanctifies us we live for his desires and not our own. And God does not want us to escape this world (John 17:15-17), but rather to let God complete the transformation (2 Corinthians 3:18), and possibly help others in their transformation as well.
The apostle Paul wrestled with this while he was in prison awaiting trial, not knowing whether he would be put to death or released (Philippians 1:21-24). (Thanks to Jon Ericson for this reference.)
For to me, living is Christ and dying is gain. If I am to live in the flesh, that means fruitful labor for me; and I do not know which I prefer. I am hard pressed between the two: my desire is to depart and be with Christ, for that is far better; but to remain in the flesh is more necessary for you.
And that's why we can't "just accept Christ and then off ourself [sic]". Even if we may want to skip the hardship and go to heaven right away, becoming a Christian means giving up what we want and giving in to what God wants.