These are all moments that we could be saying hello, giving a smile, or striking up a conversation with someone. We avoid those times because it is easier to stay to ourselves than reaching out to someone and making ourselves available. But, you never know when you may provide that moment of inspiration that someone else need - that kindness that could change the direction of their energy that day. And, what's the harm - the worst that can happen is that you don't get a reciprocal response. Is your day ruined? No, actually, you'd probably laugh a little about it.
In addition, you never know when that person next to you may have been put on your path for a reason. For example, perhaps you are looking for a photographer for a project, but haven't found anyone you like/will give you a good price. Strike up a conversation with the person next to you in line to find that he is a photographer, and he thought you were kind, so he offers you his card and says he'll discount your project.
Those types of interactions happen EVERY DAY! But, you have to be open to them and not closed off, head-down, focused on some imaginary game on your smart phone.
Look for one opportunity to talk to someone - and take a chance and strike up a conversation today. You never know what could follow... happy mingling!