It has been a very exciting beginning of a new year for the markets. The January effect is in full swing.
I think it is always smart to listen and pay attention to "seasoned" investors such as Sam Zell who is old enough to have been through multiple up and down market cycles. Learning vicariously is an important trait for those who succeed in the market.
One trait you'll hear from Sam, well as, other famed investors such as Buffett is that they are self effacing. They have an in depth knowledge of markets with all their experience, but Sam clearly says he doesn't know for sure. He can only say from his experiences that the market is likely overheated. I think it is something to seriously take into your calculus of the current market environment.
I regularly experience these types of situations with my 20 something year old kids. I might say that something they want to do might not be a good idea. Unfortunately, they don't always heed that advice, do what they want to do anyway and experience pain. It takes a lot of cycles of this for them to learn to consider the value of experience.
The market is no different. Listen carefully and consider all the information before you leap. You don't want to "walk out in traffic"!