Do you remember being in school and learning: "Every action has an equal and opposite reaction?" I do, and I think that I've applied it to all of life since that day.
Just kidding, sort of.
I think a lot of us, myself included, have the tendency to feel entitled. We are entitled to this-or-that kind of service in a restaurant, common courtesy from strangers, not having to wait in long lines at the fabric store (Grrr, Joann's, get it together!), free healthcare (don't get me started), or for whatever we think is "fair." If I feel that I've been slighted or haven't gotten my due, I can react with an "equal and opposite reaction" and competely justify it in my mind.
I act grouchy and cold to the lady at Joann's because she was on the phone to a friend and the line was kept waiting half the day. My husband accidentally steps on my foot, I respond angrily.
The problem is that I'm not entitled to any of these things. As people of God, we are commanded to humbly consider others better than ourselves and "look not only to our own interests, but also to the interests of others." (Phil. 2:3-4), but nothing in me is deserving of special treatment and I shouldn't try to demand it from anyone else. In fact, I'm supposed to be a servant. To give up my place in line to an elderly person (even though I'm trying to placate a fussy toddler who is eating the stickers off of my spools of thread), to respond sweetly to my husband when he swings the baby around and P's huge head knocks me in the eyebrow (I had a very large bruise for a very long time), to smile at the person giving me the evil eye for taking pictures in a restaurant.
In short, I need to NOT have "an equal and opposite reaction." Thank God that He decided to extend grace to me even as I betray and hurt the Savior with my sin countless times every day, He went to the cross for me. Rather than the death that I deserve, Christ took my judgment upon Himself. He "made Himself nothing, taking the very nature of a servant, being made in human likeness. [...] He humbled himself and became obedient to death--even death on a cross." (Phil. 2:7-8)