I forgot to get some cashews when I went grocery shopping. I needed them for a dinner I was making for the week, but instead I am just going to skip using them. I will make the recipe without them, since it really doesn't matter whether they are there or not. I will save money and save a trip to the store.
Last summer, I went to a baby shower. The person who hosted the gathering forgot to get the drink. She was stressed out and was going to go to the store after the shower had started to get the drink. Several people encouraged her to just forget it. We just ended up having water instead and no one cared either way. What mattered was being together as friends celebrating the birth of a new child.
Too many times we stress out if everything isn't perfect. Give yourself a break and just skip something next time you find yourself short. People can eat chips without dip or chili without meat. Your children can be happy with three presents instead of four. In the long run, it really doesn't make that much difference.