It’s scary. It’s especially scary for women, whose careers are almost invariably set back by having kids in their prime working years. But it’s scary for men too. Because when we say “work/life balance” what we’re really talking about is tradeoffs.

Spending time with your kids costs something. It costs money. It has opportunity costs. Even if you work for yourself and run your own business, the time you spend at home is time not spent at the company–it manifests itself in revenue not earned, new ideas not had, just like for the career person it’s shown in missed meetings, or in being passed over for promotions or new projects.

So it’s a scary question then: What is the balance? How much time should we spend? There is no general answer but perhaps this rule could help: Give your kids more than you are comfortable with. Make a schedule that scares you a little bit, that feels like it’s costing you.

There is a great clip we posted on Instagram a while back of the actor Michael Keaton, talking about his decision to take a break from movies while his kids were young. He was saying, as we said here in an email recently, that you’ll never regret the time you make for your family. But plenty–in fact most people–do regret all the hours they spent at the office. They regret how consumed they were by work, by goals that don’t seem to matter so much as the years went by. But no one looks back on their life and says, “I had too much fun with my kids.” “We took too many trips.” “We did too many bedtimes together.” “I saw them too much.”

So as we design our lives and make our day-to-day decisions, let’s err on the side for which we cannot error. Let’s prioritize our family–let’s do it so much that it scares us a little. It’s the safest bet you can make.