If your steak turns out tough and chewy, it's probably overcooked. Make sure to monitor the steak as it cooks and remove it from the skillet as soon as it registers 145 degrees F in the middle for a medium steak. It is highly recommended that you purchase a meat thermometer for this reason. Marinating steak in a combination of salt and acids also helps in tenderizing the meat. The balsamic marinade helps break down the steak's proteins to create a softer, more tender piece of meat.