Here is a quote from Thanissaro Bhikkhu found in epublished Dhamma Talks, vol. III (here):
"Sometimes you say something a little bit harsh to someone else and they hardly notice it, but you feel it. It hurts."It has been a while since I have sent somebody an email or called them on the phone to give them an explanation of meaning concerning something I may have said. I made a conscious decision to cultivate a strong effort not to send emails or make phone calls in a certain state of mind. Even if something I may have said needed more clarification in order for a greater understanding to be reached, that clarification would not be achieved under the auspice of a concern only for my well-being and peace of mind.
What Thanissaro Bhikkhu is talking about here is the fact that once you start to cultivate concentration, it may seem that your own actions are beginning to be more intense or powerful. However, what is actually going on is that you are much more aware of it.
I feel that it is important to remember this.