I’ve been thinking about a forensic investigation technique lately—and not just because I like reading mysteries. No, it’s because I recently came across Dr. Edmond Locard’s principle of exchange, which states, “Every contact leaves a trace.” This principle is the basis of forensic science—trace evidence, such as fingerprints, DNA, footprints, or fibers, can now be used to link people or objects to crime scenes.

Every contact does leave a trace, and not just forensically speaking. The people around us, and what we allow into our surroundings and our minds, leave traces on us and in us. We all have people in our lives who inspire, energize, and encourage us, and thank goodness for them. We probably also know people who drain us of energy or leave us anxious and irritated after every encounter. To protect our happiness and overall mental state, we can seek out the people and things which lift us up, while minimizing contact with the people and things which leave a negative trace.

I try to walk the line between hiding from the legitimate problems in the world and allowing them too much space in my head. I know what I choose to read and to watch leaves a trace, so I don’t choose to read or watch certain things, no matter how worthy they might be. I surround myself as much as is in my power with things I want to leave a trace on my world. My office especially is a place that holds symbols and talismans of inspiration, as well as reminders of love others have shown me, and things I aspire to.  I’m also fortunate enough to have a great deal of control over the people I interact with, and therefore most of them leave positive traces.

What about the traces we ourselves are leaving? It bears remembering that we have the power to influence others with our words and actions.  After all, happiness is contagious.

With every interaction, we touch others and they touch us. What kind of trace will you leave?