I think there's a subtle, nautical metaphor Epíkouros encrypted here.
I'm looking at the active particle (in the dative singular) τῷ ἐκπίπτοντι (tõi ekpíptonti), which Bailey translates as "him who errs". The phrase is referring to "the one doing the ekpíptō-ing", or "the one falling out of...", as in "...out of a boat", for example, "being cast ashore".
With this in mind, consider the second part of the prepositional phrase διʼ ἀοριστίαν (di' aoristían) that Bailey translates as "through excess". The word ἀοριστίαν (aoristían) comes from ἀ- ("not") and οριστικός ("definite"), which is the root word from which we receive "horizon" and "horizontal".
So, "the one doing the ekpíptō-ing" is doing so διά (diá) "by way of", "on account of", or "due to" something being "indefinite" (for example, a boundary, limit, or horizon). If there aren't any lighthouses, and the captain views an indefinite horizon, the boat is likely to crash.
I think he's calling someone who can't "live simply" a trainwreck, or in this case, a "ship-wreck".