My daughter learned to sit independently, but sometimes forgets that t…

My daughter learned to sit independently, but sometimes forgets that there's no support nearby and just lies down trustingly and of course hits against the wall, then sits on the floor it will hit sharply and hit the floor, then on the plastic toy it will lie down as if to protect from these blows? Have you tried soft helmets? Do they help? If she hits often won't there be headaches? I'm trying to fall like this to imagine how painful it is and it's quite painful ?