Do you believe that human nature is to be easily unsatisfied as opposed to being content?

The context of my question is, how do you plan to guard against becoming unhappy again with your current lifestyle?
Absolutely. Happiness is not enough. And happiness is transient. I'm convinced you need a certain amount of randomness, excitement, and pleasant surprises for life not to get boring. You need to have something to look forward to. So this is my guard: to keep taking prudent risks and embracing unpredictability rather than trying to squeeze it out of my life. One of the nicest feelings in life is going to sleep looking forward to what the next day will bring (positive surprises). I don't think this feeling wears off.