We all know that diamonds are the hardest substance known to man, but a diamond can scratch another diamond. Don't store your diamonds together, or they may mar one another. It is also best that you not store other jewelry with your diamonds as the diamonds can easily scratch other stones and metals.
Never wear your diamond jewelry while doing heavy work. Points are vulnerable to chipping, even during everyday activities. This is also another reason why visiting a professional jeweler every six months to have your diamond's mountings and settings checked is so important.