If we are impatient, what's our rush? Why are we full of discomfort and angst? Maybe we're hungry. Maybe we're tired of sitting, but we are where we are, and usually there's very little we can do about being there... if we are waiting... except for storming out in a big huff and not getting through something we need to get through. The truth in its most basic form is that when we are unhappy while we wait it is because we don't want to be where we are. We are resisting what is. It's the resistance that creates our tension, not the waiting itself.
Acceptance is the answer. Stopping fighting whatever situation we find ourselves in will give us instantaneous peace. This is true with lines, with people, with ourselves, and with life. It's not the situation that's the problem. It's our not liking it. It's our wanting it to be other than it is. If we calm down and take a look around, and become quiet in our minds and listen, there is a certain peace always available to us, and it comes from inside. So whatever we are stuck in may not be what we would choose, but it has chosen us. We can resist it and be miserable and tense and angry and unkind, or we can go with the flow and trust that whatever it is will fill its time and place and then will pass away. It's our choice how we handle it. It's our internal state that pays the price if we resist.
I choose a patient, playful attitude for the day's situations. If I find myself getting tense and edgy, I take a deep breath and stop fighting what's happening. I look around and let it all be just what it is.