How do I get better at handling complex periodontal cases?

You have grown steady with most patients, and now the hard periodontal cases are the edge you keep bumping against. That is a good sign, not a bad one. It means your ordinary work is solid enough that only the genuinely difficult still challenges you. The edge is exactly where skill grows next. Complex cases get easier with focused reps and honest study, not with more general practice. Treat each hard case as a chance to learn one specific thing. Ask a mentor to look over a tricky case with you, or read up on the pattern that stumped you. Depth in the difficult comes from deliberate attention to it, one case at a time. After your next complex cleaning, take five minutes to note what was hard and what you would try differently. Over months, those notes become real expertise. You are not stuck. You are standing right at the place where a good hygienist becomes a great one, and the only way through is straight into the cases that scare you a little.