Taken from elephantjournal
In Buddhism, we talk about the Three Poisons—greed, aversion and delusion.
These three poisons all come from within us and they cause a lot of our suffering.
When we are guided by these poisons, we are causing ourselves to suffer.

The first poison is greed or desire:
I want, I need, give it to me, please, please please I really want it. I need to get it and I need to figure out a way to get it.
Maybe I can just take it. Greed interrupts the natural flow of things.
Adding my desire into the equation of life, trying to change or alter the way things are to bring me satisfaction, ultimately can lead to suffering.
We often want things that we don’t need and we sometimes want them so much that we get upset. We also sometimes want things that are incredibly unrealistic.

Aversion or hatred is the second poison.
Aversion is essentially rejection—get that thing away from me.
Hatred and aversion arise in response to something we don’t like or want to happen to us. It often leads us to push away, at worst culminating in violence.
Hatred and anger can overwhelm us, causing us to act in negative ways in order to get relief from these feelings.
Sometimes, pain can’t be avoided, of course, but we make things worse for ourselves when we get angry or stressed out about it.
Obviously bad things are going to happen and we want to avoid them and we should try, but at the same time, we shouldn’t become obsessed about bad things.
We tend to worry about things that are unrealistic too. And we tend to magnify things. If something bad happens and we get angry, we are making ourselves suffer more.
Anger doesn’t help. It only contributes to our negative feelings. 

The third poison is ignorance or delusion—this poison follows directly from the other two.
Our greed and anger leads us to a sense of separation. To live with that separation I make up a story or narrative to explain who I am and why my greed and anger are justified.
More and more of my true self is lost and I live in the dream of my narrative.
 This is a fundamental delusion. The more rigid we become trying to justify and bolster our story, the more we suffer, and the more we cause suffering for those around us.

So what can we do about this? Awareness. Moment-to-moment awareness is what we talk about in Buddhism.
If my mind is here and now, living in this moment instead of in some kind of delusional fantasy, then I am not polluted by the three poisons.
Things are going to happen—the universe is going to unfold however it unfolds. We can’t control everything. The only thing we can really and truly control is ourselves. We can control how we respond to things. Sometimes, it can be very difficult.

Understanding our own actions and responses is the first step in getting out of our own way. It is a big step. If we practice meditation, we can learn to be more aware of our minds. This is important.