Stocks have a tendency to rally further than anybody thinks, and animal spirits could continue rewarding being long, but rules governing risk control will be key when the music stops, so investors ought to be planning exit strategies now, while the going is good. If they don't, the risk of reacting emotionally to volatility could lead to whipsaw decision-making and losses.
Everybody's investment style is different, but investment rules are a common theme among successful investors. Rules vary, but those governing risk control often focus on reducing leverage, shrinking position size, limiting losses, and hedging.