Our relationship to money changes as we get older. So do the mistakes that we make with it.

Every new stage of life brings new financial strategies we need to follow. And at every stage we find new ways not to follow those strategies, costing ourselves money and jeopardizing our security.

What’s more, economic and demographic changes ensure that those mistakes aren’t static, so that the mistakes of the current generations aren’t the same missteps that their predecessors struggled to avoid.

For instance, when we’re first starting out in our careers, we need to be aggressive with our investing so we can build a nest egg that grows over decades. But research shows today’s 20-somethings hold back on investing or make very conservative moves, because they’re uncomfortable with big risks.

Meanwhile, these days more people are waiting until their 30s to take big plunges like marriage and children. That means a lot of complex financial questions piling up all at once, and many opportunities to mess up. In their 40s, people often fail to pay down a mortgage quickly enough, leaving them covering the costs into retirement. And they don’t pay enough attention to how college expenses—or the cost of providing for children and aging parents at the same time—will affect their finances.