I feel so bad

I feel like such a terrible mom! Our little girl is almost 5 months old and she's getting to where she wants to sit up or have me hold her hands while she stands a lot, so I was letting her stand on the floor it's wood and she started losing balance so I let her sit and I always support her because she can't sit well by herself yet but she's getting there well she had a good balance for a minute so I took my hands off of her to let her balance on her own for a minute but I always keep my hands right by her because I know she'll start to lean/fall forward or to the side but this time she plopped down so I fast I didn't grab her in time and she hit her head on the floor.. I know every mom has those moments where an accident happens but I feel like such a terrible mom for it, she was so shocked at the feeling of getting hurt and I wish I didn't take my hands off of her for even a second but she had it for a minute and that's how you learn to do things with support and then less and less until you can do it on your own.. she's really strong and able to do so much in such a short amount of time and I love her so much.. I just can't get over her hitting her head and being so upset from it.. it wasn't that hard of a fall and she got over it pretty quick after I gave her lots of love and let her look around out the window but omg.. I feel sooo freaking bad.. I just needed to share this because I feel so upset for it..