I think that there is a misconception about negativity, in that many people oversimplify it to mean you should always be positive.

Negative feedback is an essential ingredient of all stable systems. It is the way our body maintains balance. Without negative feedback, life would be impossible.

Pain is a form of negative feedback. It is nature's way of telling you something is wrong, and that you need to change direction. It can be as simple as the pain that prevents you from touching a hot stove, or as intricate as the unsettling "off" feeling you get in your gut when you sense that someone is being deceptive with you during a conversation.

The reason "being positive" is encouraged so much is because many people have strong habits of thinking negatively. That kind of negative thinking is just a ball and chain around your ankle.

But that doesn't mean that you attempt to avoid pain or negative situations entirely. Instead, you use the negative experience to help you realign with the positive.

I don't think negative energy is necessary for growth but in order to learn, grow and expand we do need challenges. Often these challenges can seem insurmountable and as a result we often let them deplete our vital life force or turn our energy negative. The more we can endeavour to look for the solution within the challenge or perceived problem, the more we are able to deflect the negativity and turn it into a positive force, and the challenges or problems then become opportunities for growth.

Michaela and Vesuvius have great answers already so I'll take this a different way:

Don't look at negative things that happen to you as being negative. See them as lessons that make you better. An old quote that always pops in my head when something goes wrong is "That what dosen't kill me, makes me better".

Also, negative emotions such as anger don't really have to be negative. Anger has a purpose, the next time you are feeling anger, use that to really accomplish something you've been meaning to do. If an emotion didn't have a purpose evolution would have weeded it out.

Can't add anything to the marvellous answers given above except to draw ones attention to the yin yang symbol and the supposed duality of the world we live in.

I could be argued that too much 'good' is just a bad as too much 'bad' - it is in the search for equilibrium that we evolve.

When i was 2 yrs old i ran across a fairly busy road at a theme park, as i crossed and reached the other side happy and giggling i felt an almighty sting on my backside as my dad smacked it hard and growled angrily at my shocked face "that is a no, never do that again". I did not fully understand exactly why i received such a negative but i have never been run over by a car and fully understand the need for that harsh lesson now that i am older and even more-so now i have children of my own. When you first drink alcohol generally you have minimal negative affects, but after years of consumption those negatives increase and you accumulate negatives the list may read- 10 arguments, 1 or 2 physical injury's or scars 2 friends lighter. As you hit 20 years maybe a driving ban or another life changing experience to add as well as other possible negative experiences. The list of negatives could have been avoided if you did what you said you were going to do after experiencing that hangover for the first time that immortal and regurgitated phrase "I'M NEVER DRINKING AGAIN" Negatives can be a tool to help us stop the things that do us harm, they can aid us in our quest to find inner peace, the trick is heeding the warning. some of us need few and subtle negatives,some require escalating negatives and other just one quick smack does the trick to help us learn the lesson.