I hesitated to share this because the gods know SEOs have endured more than enough bashing recently. But is an SEO writer I trust deeply; he's not some random basher or "SEO Is Dead" headline grabber.
What he speaks to in this post is a perception of SEO's having a massive inferiority complex these days (perhaps brought on in part by all the aforementioned bashing and "SEO is dead!" proclamations), and that perhaps they overcompensate for that feeling by claiming to be and do more than they can (or should) deliver.
To be humble for me means that an SEO is ready to listen to his client and is ready to put himself apart if something can be better promoted using another marketing channel, being at the same time ready to offer his own perspective and so giving the opportunity to obtain an even greater success.