This week, millions of students will return to campus for another year of college. What an exciting (and expensive!) time in life. The average 2014 graduate who took out loans owes $33,000; all together debtors nationwide owe more than $1 trillion. Recent reports have shown that graduates with college debt are sicker, sadder, and face financial troubles like delayed home ownership and even delayed marriage.

Even though borrowing for the sake of college is often called “good debt,” because it’s viewed as an investment in human capital, we still ought to apply one of the most fundamental financial principles to paying for college: Avoid debt if you can.