Sweet spots
Each sailboat has a windspeed range that it "likes" - for some, it's 5 to 8 knots, for others it might be 15 to 20. Boats that like less wind are said to be tender because they heel easier and react more quickly to the wind. A "tender" boat is not a bad boat - on a light air day it can run off and hide from a boat that is stiffer and able to handle much more wind. If you are sailing, say, a "Northshore 31" that's at its best in 12 kts of wind, then for any wind speed below that you will be trying to use every bit of the wind to power the boat, and you will not be worrying much about how much it heels up to that point because it won't heel excessively. Contrast that with a "Sunnyside 28" that is at its best in 8 kts of wind. For winds above that strength, you will be trying to trim the sails so as to bleed off some of the power and not be "overpowered" - heeled too much, heavy weather helm, etc. So 10 kts of wind will be, in a sense, too much for the latter boat but too little for the former (to perform at their absolute best.) Many good boats, like your Ericson, feel a little tender at first when the wind gets up, but they settle into a groove and go very well unless the wind REALLY gets up. 12 to 15 degrees of heel is pretty normal on a breezy day, more than that might make the boat feel like it's really going but it's actually slowing down. Sometimes, like when you are racing, you will have a little too much sail up for the gusts and in a blast the boat might heel enough to take water over the cockpit combing. If there aren't any fish in the water, don't worry too much. The boat can take more than you can.