If you are past 40, a phenomenon will take place (if it hasn't already) where you will wake up one day and wonder "What's next?" This time of questioning has become fondly called a mid life crisis. I don't think this mid life question needs to be a crisis, but as a society that loves to ignore the obvious, you will have a major shift in your mid life. How you choose to handle it, will determine if it turns into a crisis or not.
The reason why this "something" happens in your mid life has to do with a number of factors. One factor is the normal course of events that take place in a person's life. You finished school, launched a career, married, had a family, bought a house and added to your financial burdens. You gained momentum along the way and received promotions, upgraded to a nicer home and maybe have the kids in college. These are the things our first major adult dreams are made of. When you more or less have them checked off your to-do list, the natural reaction is to wonder what the next big thing is in your life.
Another factor for this shift at mid life is that now we are the well seasoned life travelers that we are, we also shift from "having" to "being". Having is mostly about having something in your life, like I mentioned above. The "being" part is now about what kind of person are you being or becoming. This concept is a bit trickier to grasp, so stay with me on this. Being is a verb in this instance. Being is about you BEING a more loving person and wanting more out of the relationships, or enjoying the work you are doing. It's at a more visceral level within a person and not always so easy to identify. That's how the crisis comes in. That's when the guys hit on the young babes and the red sports cars and the women dye their hair. Clearly, not complete lists of reactions, but hopefully you get the idea. I will separate out the concept of how to identify what these signals are from how NOT to react.
Here are my pearls of wisdom on mid life change. Know that it will happen to you, whether at 41 or 59, it happens to us all at different times. Because of where you are in life, it can move you in directions that can exceed your wildest imagination. No, the younger crowd hasn't cornered the market on excitement. We have much more freedom - fewer hang ups. Be patient with yourself and the process for change. Nothing great was accomplished over night. Learn to dream all over again.