"You have heard that it was said, 'You shall love your neighbor and hate your enemy.' But I say to you, love your enemies, and pray for those who persecute you, that you may be children of your heavenly Father, for he makes his sun rise on the bad and the good, and causes rain to fall on the just and the unjust. For if you love those who love you, what recompense will you have? Do not the tax collectors do the same? And if you greet your brothers only, what is unusual about that? Do not the pagans do the same? So be perfect, just as your heavenly Father is perfect." (Matt.5:43-48)
There are some people who object to reading that last sentence as a call to a perfect "holiness," a striving to live completely in union with all of God's commands and to bring our interior thoughts into union with them as well. They point out that, in the context of this passage, perfection means being perfectly forgiving, not all hung up on rules, etc.
Alright. My problem with that is that it portrays forgiveness, true heartfelt forgiveness of someone who has wronged us - stole from us, physically assaulted us, betrayed his/her wedding vows - as somehow easier than getting ourselves to Mass every Sunday morning, or avoiding drinking too much or "going too far" in the backseat! And that's hilarious to me. When Jesus uses forgiveness as an example of what it means to be perfect, as God is perfect, He set the bar as high as He possibly could! We can't do any of it without God's grace and the action of the Holy Spirit, but the "rules" are pretty simple comparatively speaking. Now, I'm not counseling myself or anyone else to become neurotic about small, daily failures - God is literally infinitely patient with and forgiving of His children. But lets be honest about what we're called to - that “holiness without which no one will see the Lord” (Heb.12:14).