The popular explanations have always been a tad childish (i.e. "because he having the same emotion as other humans at a funeral", "because how ugly death is", etc.) Thus far, Stephen Tong's answer's the best one. I have come across someone else (Dirk) giving similar reasoning to Tong's, but such is rare.
Tong starts with the common theme between miracles and crying by our Lord, that it was never for His own sake but others'.
3 times the Bible records Jesus wept: John 11:35, Luke 19:41, Heb 5:7
John 11:35 is most well known and probably the most misinterpreted. Tong liked the reason to John 11:53, that He cried for the suffering of the stubborn hearts that took counsel together to put Him to death since that day forth.
Luke 19:41 is obvious, for Jerusalem.
Heb 5:7 doesn't indicate the specific. Tong believes this was in Gethsemane.
However, all there could easily share one familiarity, that Jesus cried for sin, not death: That how the world rebel against God, that the sin of mankind has become so grievous, that men do not understand the wrath of God that has come upon them.
Jesus was not recorded to laugh. But rejoiced on several occasions. So, it's very likely that he laughed. And one time recorded to be singing (Mark 14:26) praises, which Tong said to be Psalm 118, the passover hymn that all Jews sang, while sung generally in joy, Jesus must have sung it in both joy and sorrow, a paradoxical emotion no one can fathom: