In Matthew 5, Jesus points out, "You have heard, "You shall not kill..... But I say to you that everyone who is angry shall be liable...."
The commandments of God not only rule our actions, they are also directives for our emotions and our attitudes.
A Christian can never simply ask, "Am I guilty of a violation of the law?" The simple fact that another has raised the question of our transgression means that our mood and our interaction has not been consistent with God's instructions to be at peace with one another.
Lest you begin to think, "This is too much...." remember God's gracious and forgiving nature. More to the point, abandon the notion of God as some litigious keeper of a tally sheet. What God seeks is a change of heart and a renewal of spirit - that transformation in which we are motivated and guided by one simple commandment - to love as we have first been loved.