Presumably from the way questions have been framed, it's likely for that gravity that you underpitched (a beer this gravity would need a fairly big starter) and underaerated (again, a beer this gravity is a little to high for aeration period, let alone just shaking, and would probably benefit from pure oxygen). If you made a big starter and used pure O2 and a stone, then go ahead and disregard.
The problem with using extract for Belgian beers (again assuming you used extract) is that extracts are designed for "average" fermentability (some more fermentable than others), and you can't control it. With Belgian beers, it's often tough to get the attenuation that you want. A Tripel should finish WELL below even what the recipe stated (I like them ~1.008-1.010 or so, nice and dry). But if this was an underpitched, underaerated extract beer, I'd say you're done where you're done. Going forward, reduce the extract and add an equivalent gravity's worth of simple sugar after fermentation starts to die down (rather than adding in the boil, after fermentation really slows down maybe 4 or 5 days in, dissolve in as little water as you can, boil a few minutes, cool to room temp and add to the fermenter). That'll really help you dry it out to where it should be, as well as reducing the size of starter and aeration needed.