Honestly, I don't do anything after lose my capital. But few thing i do so that is why i lose that trade what the wrong and i realize that and make a new plan for next trade to do so I won't lose any more from trade market. I do stop trade for few hours and I wait for the perfect time to make trade in Forex trade market.
If your capital is lost and you don't have immediate access to fund your account again, definitely you have to wait until you are able to raise another money, in the meantime it will be better you keep practicing, you could also use that opportunity to learn the reason for the margin call and think of ways to prevent that later.