See that the President, the Cabinet and staff are informed. If cut out of the information flow, their decisions may be poor, not made, or not confidently or persuasively implemented.
There are known knowns. These are things we know that we know. There are known unknowns. That is to say, there are things that we know we don't know. But there are also unknown unknowns. There are things we don't know we don't know.
Treat each federal dollar as if it was hard earned; it was - by a taxpayer.
One of your tasks is to separate the 'personal' from the 'substantive.' The two can become confused, especially if someone rubs the President wrong.
Be able to resign. It will improve your value to the President and do wonders for your performance.
Public servants are paid to serve the American people. Do it well.