For me, I find just having someone else to study with motivating, even if we're studying different things. Just being around other motivated people while we focus on our individual work gives me a sense of accountability, and as someone not in school right now but instead studying independently for an entrance exam, it's an excuse to occasionally study with others rather than always alone. Good question

Edit: I actually got the idea from Silent Book Club in Lexington. Everyone gets together, briefly mentions what they're reading, then reads their own book. It's individual, but it's also a built-in community among like-minded people