tough love

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The use of strict disciplinary measures and limitations on freedoms or privileges, as by a parent or guardian, as a means of fostering responsibility and expressing care or concern.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun idiomatic The compassionate use of stringent disciplinary measures, to attempt to improve someone's behavior.