When zemerson declares that "a new person is to me a great event and hinders me from sleep" what does he mean?

He is apprehensive if this friend will truly be a kindred spirit or simply just a person to who will pass a few hours with him,

"A new person is to me a great event, and hinders me from sleep. I have often had fine fancies about persons which have given me delicious hours; but the joy ends in the day; it yields no fruit."