"Don't expect anyone else to support you. Maybe you'll have a trust fund. Maybe you'll have a wealthy spouse. But you never know when either of them might run out"

This quote is a suggestion to be independent and to not depend on anyone else to support you. Mary Schmich is suggesting that although you may have a trust fund or a rich spouse, you ought to not rely on them for your monetary security. You never ever know when either of these incomes may go out, so it is essential to be prepared and to have a plan for monetary stability. It is necessary to be self-sufficient and to have a prepare for your own monetary security. This quote is a pointer to be prepared and to not count on anyone else for your monetary security.