In the play As You Like It by William Shakespeare, there is a quote which refers to our busy but temporary lives here on earth. The quote reads "they have their exits and entrances, and one man in his time plays many parts" is from Act 2 Scene 7. Here Shakespeare is likening each one of us to an actor living out our lives like a part in a play. Some doors and opportunities will open for us and some will be closed. No matter, Shakespeare is saying, there will be other parts, other days. We shouldn't get too hung up on missed chances and failures, because there will be other "parts" for us to play. These could include student, employeee, professional, new dad, new mom, house owner, trophy winner - there are hundreds of roles in life we can fulfil.
What this speech in general is saying is that people are only temporary beings. We have our entrances and our exits -- we are born and we die. But we are not eternal like we tend to think we are.
Even while we are alive, it says, we are not the same person all our lives. We are many different people depending on what stage of life we are in. Jaques lists seven stages of life that he says we go through, each different from the last.
So the idea is that who we are is only temporary. It changes even when we are alive, and then we die.