With the regular coaching playbook it is easy to get sucked into the black hole of the same monotonous drills day after day, practice after practice. In reality, creativity - not monotonous repetition - is the key to building strengths and overcoming weaknesses. Consider the two main pitfalls that lead to plateau:
1. You practice a drill that you are comfortable with.
Got flashy looking roll tacks? Then you're probably not getting a lot out of tacking on the whistle. Dusting your training partner in every acceleration-on-the-whistle drill? It's going to be hard to notice small improvements if you're consistently the first one out of the gates. When looking to build on your strengths, instead of repeating an easy drill that you have already mastered, try something completely different. Sail with your eyes closed and try to make it around your coach using only whistle signals to find the mark (best with an inflatable coach boat!). Try to keep the boat stable while sailing heeled to windward as far as possible without taking water over the rail. If you're working on tacking, try your tacking on the whistle without the crew wearing a harness. If that's too easy, see if you can tack with the crew crossing the boat in front of the headstay. To work on down speed maneuvers (like accelerations), try sailing around a buoy without ever being on port tack.
If you mix in drills that force you outside of your comfort zone, your foundation skills will improve a lot.
2. You practice a drill that pulls your focus in too many directions at once.
So on the surface, tacking might seem like a pretty simple skill, but consider the ingredients of a good tack: feet in the correct spot, smooth movement into the boat from the wire, consistent unhook, good timing between skipper and crew, fast hand switch, precise sail trim, precise weight placement, and much, much more. If you're having trouble executing the perfect tack (and trust me: you are...) single out one skill to perfect before you move on. One of my favorite ways to do this is to create simple drills that emphasize one aspect of a technique. For example, if you are having trouble breaking the habit of clipping in before you are at full extension on the wire, practice hanging, and counting to ten after each tack before you clip in. If you are struggling with your hand switch, practice completing the tack with your arms still crossed (i.e. don't do any hand switch at all). Sail the boat perfectly for twenty seconds steering with the tiller behind your back and allowing the skipper to trim main, until the boat is back to full speed, and then switch hands.
There are tons of creative drills like these that can help isolate your issues, or bring a new aspect into focus, so don't get stuck doing the same thing every day!