I'm a firm believer that your words have power, that what you say and think goes out into the universe and will come back to you 10-fold. Because of this, it's super important that you make sure that your thoughts and words are filled with positive intent so that you can bring positivity back to you. When you think in a negative way, it's often reflected in your actions and words. This is why you need to keep your thoughts just as positive as your words so that there aren't any ill effects on your actions. People don't like to be around negativity, so keep pure intent and positive focus through your thoughts, words and actions, because people can intuitively feel your energy.
Since I believe this, I try very hard to not say or think negative things that might come back to bite me in the butt later. That doesn't mean I never complain or get upset. I can get upset like anyone else, but when I do, I try to find my focus and bring my soul energy back to center and then infuse it with positivity by saying something to balance the negative things. Negative thoughts hold the same power as negative words. I try to stay positive in my thought processes as well. I'm also grounded, so I understand there will be days when I'm overwhelmed with negativity from other people or frustrated with situations. When this happens and I fall into the flow of negativity and lower my frequency, I try to recognize this right away and take steps to counteract it by doing or saying something positive. The idea is to transmute the negative energy into positive.
When you find yourself in a position of having negative thoughts or wanting to lash out at someone, look for ways to replace your negative thoughts into positive ones because it'll raise your awareness and energy. Because words have magnetic power, whatever you say will come back to you. For example, if you said to someone, "I hope you fall and break your leg!" you just may be the one to fall and break a leg. Or if you tell someone that you hope they get the promotion at work, you may also get a promotion. See how that works?
Something I always tell people who want to inflict harm onto others with projected thoughts or actions is.... You'd better make sure that it's worth it, because the same energy is going to come back to you, sometimes in stronger proportions. This is why it's better to just drop it and move on - keep within your integrity.