And establish the counsel of your own heart: Good News Translation and Contemporary English Version express this well with “And trust your own judgment” (similarly New English Bible). We should not rely completely on the advice of others.

For no one is more faithful to you than it is: The Greek adjective translated faithful is ambiguous in this context. It can mean what Revised Standard Version says: no one other than you yourself can be counted on to give advice that is more in your own interest. It can also mean, as Good News Translation has it, “reliable.” These are not quite the same things. Your own judgment may well be intended to be in your own interest, but it could be mistaken, not as reliable as someone else’s opinion. We prefer Revised Standard Version‘s interpretation, and suggest this model for the line: “no one is in a better position to look out for your own interests.” Contemporary English Version is similar with “you care more about yourself than anyone else does.”

Quoted with permission from Bullard, Roger A. and Hatton, Howard A. A Handbook on Sirach. (UBS Helps for Translators). New York: UBS, 2008. For this and other handbooks for translators see here.