This is an item from Anton Moker's Decalogus metricus et paraenetica disticha, published in 1573. You can see the book at GoogleBooks.
Medium Serva
Omnibus in rebus medium servare memento;
Immoderata nocent, sed moderata iuvant.
The vocabulary is keyed to the DCC Latin Vocabulary list. There are two words in this poem that are not on the DCC list:
immoderātus, -a, -um: unlimited, extravagant
moderātus, -a, -um: limited, bounded, moderated
in: in, on (+ abl.); into, onto (+ acc)
iuvō iuvāre iūvī iūtum: help, assist; please, delight
medius -a -um: middle, central
meminī meminisse: remember, recollect
noceō nocēre nocuī: harm
omnis -e: all, every, as a whole
rēs reī f.: thing (rēs pūblica, commonwealth; rēs familiāris, family property, estate; rēs mīlitāris, art of war; rēs novae, revolution)
sed: but
servō -āre: save, watch over