I bet you've heard the old saying, "What goes around comes around." I am a firm believer in this. I think everyone, at least to a certain extent, creates their own reality through thoughts and behaviour. My faith says everything you send out comes back to you threefold. You don't have to believe that, but bear with me here. :-)
Some people have a negative disposition. They always find something to complain about, and the entire world is against them. If something goes their way, they think it'll never last. They might even play out scenarios of why it will go wrong until it becomes a self-fulfilling prophecy. If something goes badly, it's just the way their whole life has been. (Anything good is quickly forgotten.) Alternately, they think they're absolutely brilliant, everyone else are idiots working against them, and should be complained over at great length. I think everyone knows someone like this, and try to avoid them. No one wants to be around people who just complain and bring everyone else down.
Time for a disclaimer: I'm not talking about people who are clinically depressed and might need medication and professional assistance to find balance. Seriously though, I know people who answer a friendly, "Have a great day," with a long explanation of why it will be the worst day ever. If I say, "Have a great day," the next day again, it repeats all over. In my opinion, the correct answer is along the lines of, "Thank you, you too."
The positive change must come from within. No one can do it for someone else. Sadly, the people on the negative side tend to wait for someone else to fix everything for them, and make them happy.
Other people always seem to find a smile, and have a generally positive outlook. They give off positive energy and bring others up, and people like to be around them. When something goes well, they're generally grateful, and when something goes bad, they have the ability to cope and solve problems. If they need help, friends and family are quick to lend a hand, because they're so nice.
I'm stereotyping now, of course. Most people fall somewhere between the edges of positive and negative. Still, give it a thought, and figure out where on the spectrum you want to be. Once a person begins, smiling and thinking positive thoughts grows into a habit. When you start, you might have to make yourself think, "This will be a wonderful day," but after a while the thought comes on its own.
Don't get me wrong - everyone needs to vent from time to time, but there's a difference between discussing something and whining endlessly. If people ignore you and start screening your calls, you've probably crossed the border to whining. Also, ask yourself what your complaining will do to the person you're talking to. If someone says, "Good morning," and you answer, "No, it's horrible," you might be ruining someone else's day besides your own.