Sustiene i makaka'-mo!
(Hold your itch!)
Sustiene comes from the Spanish sostener, and means to "hold, maintain, support, sustain."
Makaka' means itch or itchy.
So "Sustiene i makaka'-mo!" means : even though you are itchy, don't even try to scratch!
In other words...
You are really hungry, but the food hasn't all been put on the table yet, or blessed, but you feel so tempted to just grab and eat, and your mother says, "Sustiene i makaka'-mo!"
You are in a meeting, or in church, or at a school play, and you're tired of it, and you are fidgeting in your seat, barely able to keep on your chair, and your spouse says, "Sustiene i makaka'-mo!"
The phrase has also been used in connection with romantic attractions.