Please advise if it's a good thing when a hemorrhoid gets harder?

Not necessarily: This may be what is called a "thrombosed hemorrhoid", which is when clotted blood is trapped under the skin. If this is the case, the body usually reabsorbs it over time, or sometimes it can erode through the skin and evacuate externally. Safest course would be to have your doctor check it to make sure this is nothing more serious.