Once you open the avocado, the browning process will start as the flesh is exposed to oxygen. If you're not planning to consume the entire avocado right away, then one way to keep it fresh for longer is to leave the avocado pit inside. The flesh underneath the pit will remain fresh for longer with only a few black spots. For best results, drizzle some lime juice on top and tightly wrap the remaining avocado half in plastic wrap and refrigerate.