You do have to be careful about your grocery selections. One of my favorite boogeymen is the product called peanut spread which comes in a jar just like peanut butter and looks just like it, but it's loaded with added sugar. Of course, some brands of peanut butter are, too, but this is a thing with the high end products that you'd think wouldn't do that.
But, my advice is just stop adding sugar to recipes and stop eating stuff that is obviously sugar laden (muffins, cookies, etc). Over time, you become somewhat sensitized to foods that have it where you don't expect it. Check labels when in doubt, but basically, don't sweat the small stuff and absolutely don't refuse a small piece of your niece's birthday cake - it won't kill you.