Our LO is sitting pretty confidently on his own and doesn't like to be laid down on the floor to play anymore. Twice today when our backs were quickly turned he lost his balance, fell backwards, and bumped his head. I know I can't keep him in a bubble and it will probably get worse once he starts walking but I still feel so guilty when he topples and I didn't catch him. I'm a FTM so I have no idea how much bumping their heads is normal/ok versus something to be more vigilant and concerned about--any advice?