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C.S. Lewis commenting on happiness said that "God cannot give us a happiness and peace apart from Himself, because it is not there. There is no such thing." God knows we are unable to be happy without Him, which is precisely why He emphasized seek first the kingdom of God and His righteousness, and all these things shall be added to you.
It's simple really, and it is actually about patience. Gone for now, is a lot like gone for good. It is our own stubborn and impatient ways that make us unhappy. Are we willing to accept delayed gratification? I mean that in both the micro and the macro sense. Would we rather accept a little happy now, or the better plan God has for us for when He deems us ready? Are we unwilling to sacrifice this temporal life for the sake of eternal paradise? The choice is obvious, but unfortunately it is a tough one.