It may not be that bad to fake a smile every once and then. Happiness is one of those things that you have to pretend to do, until you are actually doing it.
Like falling asleep.
Very few people can turn a switch and declare “I am sleeping now”. Most of us lay down, shut our eyes, pretend to sleep until we are really doing it. Riding a bicycle is also alike in the beginning. You get started, wobble for a while, and pretend to be a cyclist, until slowly, you become one.
When we are in a good mood, things look positive, our interactions with other people are more pleasant, and the feeling builds in itself. Sure, there are things that can get you out of a rut and make you happy in an instant, but those are just jump-starting the process, like the slope on the road that gets you started on the bike.
To a degree, happiness is a choice we make.