Why can't you be here with me?

Why is it that we miss people more when they are there with us? Is it because we miss the person that they are and we want to be with them every second? Or is it because we wish that we could be with them and can't? I don't have the right answer but all i know is that this feeling is terrible. Cause there is nothing that i can do. All i can do is sit, and wait, wait for them to come back. But sometimes it feels like waiting for them is like waiting for rain in this drought, stupid and pointless.