Life isn't all light and fluffy. There's no guaranteed Hollywood ending and no one ever promised that it's going to be fair. There are going to be times when darkness surrounds us and is within us. To deny the darkness' existence is as dangerous as wallowing within it.
The dark doesn't matter; what matters is whether or not you choose to turn on the light.
Filter what comes in
Life just is. It can be as big or as small as you want. It can be all rosy, or all despair. You're not obligated to let it all in. Turn off the TV, select what you read. Life will go on outside you, even without you tuning in to find out what's next after the commercial break. Only let in what you want. It won't change the world one bit, but it will change your world in ways unimaginable.
Deal with what comes in
Stuff is gonna get in, no matter how hard we try... so we need to know what to do with it. Our strength is actually in what we do with what gets in.
Edit what goes out
Sure misery loves company, but just 'cause bad moods happen, we don't have to ruin everyone else's day. That will only come back to haunt us. It's better to let the light in, rather than let the dark out. Find things to brighten your day.
Do something light
Listen to music you like, go for a walk... anything that doesn't put more pressure on you.
Get rid of the Dark Makers
If there is a definite cause for all the darkness around you, work on getting rid of the source. Just doing that can save you most of the hassles.
Help someone else out of the darkness
We can't see our own problems, cause we're too close. Helping someone else out of their darkness can sometimes have amazing results for us. The advice you give to others is often the one you need to take the most.
Don't wait for someone else to light your fire
Waiting for someone else to do it is disempowering for yourself, and too much to ask from anyone else. You are the light; so shine.