The client is always right.
Even when they are doing it completely wrong, the client is always right.
Even when everything in your heart, in your body and in your personal experience tells you that their plan is destined for failure...the client is always right.
Even if you want to go the extra mile and do it better for them because you genuinely want to see them succeed, it is them who are paying you to do exactly what they assigned you to do...
The client is always right.