What's the point in spending your entire life just so you can look back in your final months and be pleased? I can't think of a reason why your happiness at the end of your life is any more important than your happiness in the middle of your life. Rather, a life well-spent is one in which the sum total of your happiness over time was at a max. That means factoring in what's important to you now, even if it won't matter to you later on.