God doesn't want us to just be happy. God wants us to be like Him.
and maybe, then, we will be happy in heaven. but God never promised joy on earth. We have a wild God. Not a tame God. not a God who promises easy things and says we should live according to our own wishes. Sometimes He says things we don't understand, sometimes He commands things that really freaking **** and we feel like the world is crashing down on us, because God never said "follow me and you'll be happy in this life." He said "follow me." He said "take up your cross."