Brush It Off - Retail

Pet peeves, everybody has them. If you work in retail, you probably have a running list of things that customers do that drive you up a wall. Let me explain:
A. Failure to return a cart to the cart corral. 
B. Failure to push a cart into the row inside the store instead of parking it next to said row.
C. Failure to remove cart from check out lane.
D. Asking for a bag with anything with a handle. Ie. milk, detergent, bleach, etc. 
E. Taking forever to pay.
F. Leaving abandoned items laying around the end cap. Just hand it to the cashier, eh?
G. Telling cashier how to bag.
H. Acting like you're better than the cashier.
I. Wanting each item bagged individually.
J. Getting mad at guest service because you waited six months to return something and now it's no longer in stock.
K. Writing a check and not coming prepared with a pen.
L. Complaining that the card reader asks if you want your entire purchase on the card.
M. Placing your basket on the floor.
N. Stating something was cheaper than it rang up for, and then getting upset when I call someone to verify
O. Rushing cashier.
P. Slowing cashier down.
Q. Going to a lane with the light off, unless told to
R. Refilling the icee when it clearly states no refills
S. Asking if the cafe is closed when the lights are turned off and no machine is running
T. Sending your child to the cafe alone
U. Allowing your child to scream their head off instead of removing them from the store
V. Giving in to said child to stop them from screaming
W. Allowing your child to sit on the bagging area
X. Having your child unload the cart, while they are still sitting in it and can barely reach the belt
Y. Having your child sign their name on your credit card
And the best one,
Z. Talking on your cell phone.

I understand that this might not seem all that kind. Let me explain further. I went on a leave of absence from working retail for about three months last year. I returned in December. Within my first week back, I saw two things that changed my perspective. One: a child begged and begged and begged his mother if he could buy a $20 gift card. The mother naturally seemed apprehensive and asked who it was for. The child stated that he did not want to say because it was a surprise. He begged some more and the mother gave in. She mentioned that she hopes she didn't just waste $20 on nothing. The cashier then handed her the receipt and she looked at him and asked if he was ready. He told her to hold on and he turned around. He then handed the gift card to the woman standing behind him and said 'Merry Christmas'. This kid was maybe eight years old. Two: I was sitting in the cafe on break. Kyle, the cart attendant, was looking very confused and looked up and saw me sitting there. He then came over and asked what he should do with what he just found. I asked what it was and he showed me a $5 gift card that someone had taped to a cart with a note saying they were doing the 26 random acts of kindness in honor of Sandy Hook. He wanted to know if he should give it to lost and found or just leave it. I told him he should just leave it on the cart, and that's what he did. These two acts are basically what initially got me thinking about doing a year of good things. There isn't enough good in the world.

Today while I was working, a woman came through my line on her cell phone. She had the man on speaker phone, even though the phone was up to her ear. I could tell that she had no intention of hanging up her phone. She then did not bother to sign the card reader and so I just hit the bypass button since she wasn't spending that much money. Then she walked around her cart and left it right in the middle of the check lane. What a pleasant woman. I returned her cart and just laughed it off. I have noticed lately that situations like this do not really phase me. Maybe it's from being in retail for three years, but it's just not worth it to get upset. I went back to my register after returning her cart and greeted the next person with a smile and asked them how their day was going. 

Pick and choose your battles because in the long run, the majority of them don't matter.

Updates: I put the card for my mail person in the mailbox on Thursday evening. It's still sitting in there and we have gotten mail both yesterday and today. It clearly states who it's for. I don't know if I should take it out and put an anonymous card on top of all the mailboxes, or if I should just figure that they do not appreciate my nice gesture and just throw it away. What would you do?