Waiting someone or something is strange. If the waited is a human you love, it becomes hard and emotional. If the waited is an order of some sort, it becomes annoying.
You lose focus, and start to think about the thing you’re waiting. It messes your work, emotions and especially your precious time. You start to think what gonna happen next when the waited arrives. But that not helps, instead you make it worse, now you really want the thing you’re waiting to arrive. This becomes a paradox and you can’t escape until the waited arrives.
My personal solution to this is: thinking that the waited won’t arrive and you have to continue your life (this only works when the waited is a human). It makes you sad, but helps you to move forward and do what you need to do. If you’re sure that the waited will arrive without you taking an action, this approach helps a lot.