Some say you should bring an umbrella with you even on a sunny day. You'll never know when it's going to rain. Although I hate carrying one myself, I do understand the need to prepare for the unexpected. Life has it's ups and downs, so no matter how smooth things seem to be, there's a chance something might go wrong. And according to Murphy's Law, if can something can go wrong, it will.
I guess the best way to lead your life would be to hope for the best and prepare for the worst.