For the sake of one lost sheep, the Good Shepherd leaves the rest of His flock, goes out, and finds that one lost sheep.
And when the Shepherd returns with the lost sheep on His shoulders, there is great rejoicing.
If I am to become a more godly person, then it seems to me that it it is hardly godly to pray for (or to rejoice in) the lost of even one soul to hell.
As others have said on this thread, better to pray for the person's slavation by a merciful, gracious God -- who, by the way, showed his mercy and grace to me when He saved me.
That is my situation and position as well. I cannot judge the status of another's soul, although I can - and should - judge the merit of their actions. I could never pray that another person be in hell, but I do hope that they're in another part of heaven far away from the part I'm in. Fair enough?