"You can only milk a cow so long, then you're left holding the pail"

This quote by Hank Aaron is a metaphor for the concept that there is a limitation to just how much one can get out of a scenario. It recommends that if one continues to take advantage of a circumstance, ultimately they will be entrusted nothing. This might be translated as a warning to not take advantage of a scenario for too long, as eventually the resources will go out and one will be left with nothing. It might likewise be translated as a tip to not rely too greatly on one income or resources, as eventually it will go out. This quote is a tip to be mindful of just how much one draws from a scenario, and to be knowledgeable about when it is time to carry on and find a new income or resources.