2 Similar situations with totally different thoughts

So I went to my favorite shopping place (Wegmans) to get groceries for a late night dinner and... ok wait... About a year and a half ago I was in Target and as I'm checking out the cashier is just being kinda rude. I walk away thinking.. "what a bitch..." After making it approximately 3 more steps the idea pops into my head that she's probably been there all day and has probably been going through her own personal hell with customers. In my head I kinda apologized for having thought that about her. If it were me... I might have acted the same way.. who knows? So tonight I'm at wegmans in the 15 items or less express lane and there's a guy in front of me with 6, 1 liter bottles of coke and in front of him a couple with approximately 45 things. First thing that pops into my head is "WTF!!! Are you seriously going to be 'those people'?" The guy in front of me clearly annoyed and making overly sarcastic comments to the female customer. Her boyfriend walks up and I flash him a look of "really...?" So the man in front of me checks out and I ask the cashier "does that bother you when people do that?" And she replies with... "Not at all." It him me that I may have been completely wrong. It might not have been the couple's fault at all. What if they walked up and there was no one in line and it was the cashier that said to come in her line. The same thing happened. I was more or less apologizing in my head to them. So quick to be narrow minded about people's actions. I felt genuinely bad about flashing them a look. She giggled about being in line with so many things but I was already perturbed a bit so of course it annoyed me. I wasn't being inconvenienced any by this. What was gonna happen? I was going to spend maybe 3 more minutes in a line with no rush to get anywhere. So my lesson today?? Maybe I should just mind my own business and not be so quick to judge. That's all I got tonight...