Luke 24:36 And as they thus spake, Jesus himself stood in the midst of them, and saith unto them, Peace be unto you. 37 But they were terrified and affrighted, and supposed that they had seen a spirit. 38 And he said unto them, Why are ye troubled? and why do thoughts arise in your hearts? 39 Behold my hands and my feet, that it is I myself: handle me, and see; for a spirit hath not flesh and bones, as ye see me have. 40 And when he had thus spoken, he shewed them his hands and his feet.
We should go easy on the apostles! It is simple, in hindsight, for us to understand and acknowledge the resurrected Savior. But it was a brand new thing for them. The Jews were a superstitious people, always seeking for signs. They had great debates as to the question of the spirit world: angels and demons; the afterlife, etc.
So when Jesus appeared to these scared and very confused men whose entire lives had just been turned up-side-down, they must have been beside themselves. Jesus spoke immediately, "Peace be unto you." Never-the-less, they were terrified and determined they had seen a ghost.
It took further admonishment and empirical evidence from the Lord to convince them they had nothing to fear. Suddenly they were overwhelmed with joy, questions and still, a bit of incredulity.
I ask you, in retrospect, with 2000 years of Christian history between then and now, why are we always so fearful? Don't we recognize that the Ghost in the room with us now is the Holy Spirit? Do we not realize that He is ever present and all is under control and there is nothing to fear? Yes, we have questions. Sure, we say, "Lord, I believe, help my unbelief." But the Risen Lord is with you, peace be unto you.