Matthew 5: 7-9 (NRSV)  Blessed are the merciful, for they will receive mercy.  Blessed are the pure in heart, for they will see God.  Blessed are the peacemakers, for they will be called children of God.
There are many instances in the Bible where God clearly spells out the character of the people He would like us to be.
In this instance Jesus is giving instruction to his disciples, and what He said then remains true for us today.
He calls us to be merciful, to be pure in heart, and to be peacemakers, and He does not say to be these things some of the time.
This passage of scripture does not say "Blessed are those who are occasionally merciful... Blessed are those who try to be pure in heart... Blessed are those who are peacemakers when things are peaceful, but fall to anger when someone disrespects them..." It calls for us to be merciful, pure, and full of peace all of the time.
God wants the very best from us, so that we can receive His best, and our lives can be a living testimony to others. When He gives us instruction, it isn't on our terms, when these actions are easy or convenient, He asks us to hold ourselves to a higher standard all the time.