Who am I?
If you ask most of us who we are, we will answer you by naming one or another relationship. We are, for instance, a husband. Or a golfer. Or a businessman. But to say we are a husband, or a golfer, or a businessman, is each case to define our self in terms of the relationship we have to something.
In contrast, we tend not to define our self in terms of what is happening with us at any given moment. I do not think of myself as someone whose shoulder is itching. Or as someone who happens to be looking at a computer monitor. Or as someone who is wishing it was dawn. All of those are transient things -- too transient for me to think of them as "me".
Yet, being a husband, a golfer, or a businessman are also transient. That is, if you really think about it, you are not simply "a husband". You are only sometimes a husband. Just as your shoulder only sometimes itches. And it is only a convention of thought that you imagine yourself to always -- or continuously -- be a husband.