You practiced—and practiced—soft-field takeoffs and landings while training for a pilot certificate. But it’s likely you never actually took off or landed on anything softer than a paved runway. The sensations you’ll experience when your airplane touches down on grass will be brand new.
Many flight schools don’t actually introduce students to landing on grass or gravel—there may not be a suitable field nearby, or their insurance doesn’t permit it. Seek out a fixed-base operator that does permit soft-field operations and get a checkout there. It may mean finding an instructor with a tailwheel airplane, because taildraggers are much happier operating on grass. So there’s a good reason to start on a tailwheel endorsement.