How to Avoid Having a Rocklike (Hard) Leftover Rice?
The standard ratio of rice to water when cooking is 1:1 (1 cup rice grains is to 1 cup of water). If you prefer a more soft cooked rice, try to add 1 more cup of water. So for 3 cups of rice, so you should mix in 4 cups of water instead of the usual 3 cups.
So that if ever you cannot consume all the rice you cooked in one setting, it will still be soft on your next meal, making it still palatable.