It’s the mantra around every Thomas train table, the refrain at every playgroup: “You have to share.” There are, of course, varying levels of success, evident in the wailing sparked by a train track to the head and all manner of other unfortunate sharing mishaps. But universally, or so we hope, parents recognize sharing as one of the foundational lessons of childhood.

It’s tempting to feel a sense of relief if you’ve ushered your child to a tantrum-free, biteless, sharing regime by the time playgroup has evolved into preschool. But there’s far more work to be done if the end goal is a responsible adulthood. I was reminded of this recently when my neighbor told my daughter she could borrow a Wii game. My five-year-old trotted sunnily to me and announced she had been given the game. Aha! A learning opportunity was before us!

A conversation about the difference between “having” and “borrowing” followed, my daughter thanked my neighbor for sharing, and I left feeling like a good parent…Yet it turns out I forgot a big part of the lesson. This became apparent a month later, with the same game now lying forgotten and gathering dust beside the television. I forgot to teach about the lesson of “contract”: that lender and borrower enter into an agreement with certain conditions…such as the time by which the item must be returned. Of course, in my five-year-old’s lingo, this would more likely be called “a deal” and sealed with a “pinky promise,” but the basics are the same.

Why is this important for my daughter? Does it really matter that the Wii game was (or was not) returned on time? Her friend apparently does not care since she’s not banging down our door to get it back, so why should my daughter (or I)?

The answer is that the issue is not about the Wii game at all. It is about teaching the fundamentals of responsibility, of setting expectations and then fulfilling those expectations. For our five-year-old, we’re talking simple stuff: a Wii game or a small (hopefully non-breakable) toy. But I know the borrowing stakes will grow as she gets older…perhaps a friend’s favorite book, an expensive piece of sports equipment, or (yikes!) the car. The point is that when she understands some basics she can then graduate to the more abstract notion of “contract and obligations”. Having learned that will help her navigate potentially dangerous situations down road.

So if a five-year-old understands the concept of sharing, grasps the basics of fairness, and is bartering with friends for the loan of a toy, then that child should be ready to understand their responsibilities in “a deal”. With some gentle reminders from Mom and Dad, of course, they should also be able to follow through with their side of a bargain.

So the small-scale borrowing and lending we begin with our friends as children is great, age-appropriate practice for the more important tasks we face later in life (e.g. large-scale borrowing and lending money, etc.) So the next time my daughter wants to borrow something from or lend something to a friend, this is what we agreed she will do:

1. Clarify the agreement (deal): What exactly is being borrowed? How long will it be borrowed for?
2. Set some terms and conditions: When will the item be returned? How will it be returned? What will happen if it’s not returned?
3. Follow through!

Even at the age of five, I know my daughter is practicing and developing life skills. It will be a long march to socially and financially responsible adulthood. Creating some structure, setting some ground rules, and honoring agreements now will not only be good for her friendships, it will be great practice for her later years when the stakes will be so much higher.

Mani Kulasooriya is an employee at the loan agreement site LoanBack.com