This is a poem by Lucian from the Greek Anthology, rendered into Latin by Hugo Grotius (1583-1645; you can see his edition of the Greek Anthology in Latin at Google Books).
Quantum vita patet, brevis est felicibus; una
Nox miseris ingens temporis est spatium.
The vocabulary is keyed to the DCC Latin Vocabulary list. All the words in this poem are on that list:
brevis -e: short, shallow, brief; adv. breviter
fēlīx -īcis: lucky; adv. fēlīciter
ingēns ingentis: huge, enormous
miser misera miserum: wretched, pitiable
nox noctis f.: night
pateō patēre patuī: lie open, extend, spread
quantus -a -um: (interr.) how great? (rel.) of what size, amount, etc.
spatium -iī n.: space
sum, esse, fuī: be, exist
tempus -oris n.: time
ūnus -a -um: one
vīta -ae f.: life