Ah, the version i know says 'don't wrestle with pigs' you'll both get dirty but the pigs will enjoy it'. A comment on getting into argurments with politicians and the like, i think

'as useful as a chocolate teapot' and 'quick, hire a teenager while they still know everything' come in handy on occasions.
But the one I really like is Roosevelt's 'do what you can, where you are, with what you've got'. I like it because it reminds me to 'get on with it now' rather than wait for x, y and z (me to be thinner, richer and have more free time

)