Someone should take their practice seriously, but not so much that they loose self-awareness or become arrogant or uppity about it. We, as humans, have limitations. Not taking yourself too seriously involves being able to poke fun at yourself and it actually empowers the person to not be affected by the opinions of others and generally further unfetters them from the shackles of society and the right hand path. Of course this can go to an extreme but the point isn't to become a jester.
This is great advice no matter who you are, thanks Mandi. =^_^=