Life is so hectic nowadays, it's almost impossible to keep it all under control. So, while I can understand how you feel, I hope you can find it within you to not beat yourself up too badly. You wrote that you're feeling guilty & bad about yourself because, as an adult, you should be on top of these things. But, at least from my perspective, perhaps the more adult thing to do is simply take this experience in stride, consider it a learning opportunity, & see what (if anything) you can do to correct the error. Here are links to 3 articles, from PC's archives, that (hopefully) may be of some interest:

When You're Overwhelmed with Being an Adult

How to Stop Punishing Yourself

Cultivating Self-Compassion