Problems with the lines - Issue 1

It is at times mentioned:
Do not major in the minors, and minor in the majors.

That is to say:
Do not take too importantly what is trivial, and to consider trival things that are truly important. Know priorities in life. Don't overreact over small matters. Don't put aside important matters. View things rightly and spend time for things which matter.

Problem:
What then do you consider important? Or more clearly, what is important and how do we know whether one thing is important or not? If the answer to the question is relative - then the quote is meaningless. Just another fancy quote. But assuming that the author believed that priorities in life can be measured, and that one thing can be more important than the other - then this quote is wisdom.