Use 'ease up on' when suggesting to slowly reduce something rather than stopping suddenly. Maybe you should ease up on the sweets instead of quitting cold turkey.
Pro Tip 2/3
Conversational Context
'Ease up on' is often used in informal, conversational settings between familiar individuals. Hey, you're driving too fast—ease up on the gas, will you?
Pro Tip 3/3
Emotional Tone
The phrase can imply concern or care, not just a command to do less of something. You've been working so hard. Ease up on the late nights, okay?