Do not withhold correction from a child. If you strike him with a rod, he will not die. Punish him with a rod, and deliver his soul from Sheol.
Proverbs 23:13-14 TLV

The purpose of all discipline is to spare the child greater pain later. If you withhold discipline because it makes you feel bad to see your children in pain, you are actually being selfish and hateful toward your children.