Look at the media; where are the stories of 'this time it's different. We are in a new paradigm'. They don't exist. just the odd 'analyst' saying 'DOW 30,000' or whatever is not the same. They may discuss chares in US cocktail parties, but no-one really is over here. Sure the markets are high. They may well go a lot higher, once 'everyone' gets on board. If you are sensible you'll have no part of all this mullarkey. However, trading is about supply and demand, not about 'this number looks too high to me so I'll sell'.