All emotions are impermanent. Your happiness will not last. So enjoy it now, dance, be laugh like a fool, laugh like a sage, because one day you will be sad. And your sadness will not last, so be sad. Cry if you must. But know that you will be happy again. All things in life are subject to change, that is why it is so important to live in the now.
"You can not get out of now. And you never will!" - Alan W. Watts.