I think the saying that only you hold the key to your own happiness is true. My problem is, it seems like everyone else on the planet seems to have the key to your unhappiness. That doesn't seem fair!
I am generally a happy person. I don't know if it is ignorant bliss or I am just a simple person. Maybe I have found inner peace that other, less happy people haven't. It doesn't usually take much to start me off on a happy note.
My problem is how others affect my happiness. If my husband is unhappy, it quickly makes me unhappy even if (and sometimes especially if) there is nothing I can do to cheer him up. Misery does love company and it usually finds it.
Simple things in your day can either keep you upbeat or bum you out. The drivers on the road can either let you merge or cut you off. Shoppers at the market can either ignore that you have screaming kids and only a couple of things in your basket or they can let you go ahead of them at the cashier. Even a simple smile when you make eye contact can make a big difference in one's day.
I guess what I am trying to say here is, keep in mind that you hold the key to others' unhappiness so be nice. It can make a world of difference. You can't make someone happy but you can help keep them there.