Fandom: Lord of the Rings (movieverse)
Legolas cannot show his true feelings at Aragorn's return, when those who love him had believed him dead.
Aragorn is promised to Arwen, and in any case, they are in the middle of a war, whose most desperate battle, perhaps, lies before them now. The time and place could not be more wrong for a declaration of love, were it possible. Which it is not.
And so Legolas returns the Evenstar pendant, as is proper, and he restricts himself to those emotions fitting for the unlooked-for return of a trusted brother-in-arms: relief, concern.
He keeps his overwhelming joy to himself.