Too Good to Be True!

So last night, right before Caylen's bath and bedtime, after we had drove home from work, her screaming the whole way, Caylen walked! Yes, she walked. At 16 months, 3 weeks, and 3 days, she walked. Yay!  My heart was so full; I couldn't even believe that she had done it!
Ok, back it up a little bit... I was so excited that I had to share right away! So yesterday, we were getting ready to leave work, waiting for Ava to be picked up. Caylen Loooooves to be around Ava!! I am guessing it was partly her who inspired Caylen to stand up on her own.
Ok, back it up a little more.... Caylen has been 'bear crawling' or 'crab crawling' for a while now. She crawls on her hands, and instead of on her knees, she is on her feet. You get the idea, right? Well, anyway, she has known how to do that for a long while, but here in the last few days, she has been deciding that she wants to either be mobile by 'crab crawling,' cruising, or walking with her walker. Given that information, I guess we are ready to go...
Soooo, I guess I can get to the standing by herself thing. Caylen has been able to stand by herself for a few weeks by now, but she always got to that point by pulling up. Well, last night, when she was playing with Ava, getting ready to go home, she went from a 'crab crawl' to standing, all by herself! I couldn't hardly believe what I saw! Then, we get in the car to go home, she doesn't want to go in her seat, cries (screams) all the way home, and we get home and chill out-- brains fried from the ride. I throw together a peanut butter sandwich for her, she eats really well, and we let her watch the Goodnight Show until it is bathtime, like usual. Well, Caylen starts doing her funny crawl thing again, and she stands up! Again, again, again.  Woo hoo! Brandon stretches out his arms and says, "Come here, Caylen" or something to that effect, and voila, she does! Like she has been doing it forever. Didn't even have to think twice. Just went. I couldn't believe it! She took at least 4 steps to him like it was nothing! Then, she proceeds to do it again, again, again. Wow!!! We have been waiting for sooo long for this! And, here it is, happening!! Right now! Well, she decides that she is tired, and she doesn't want to do it anymore, so she 'crab crawls' to the tub. Ready for a bath. I was so excited for her, I could barely contain myself!........
 Next morning (today):
I was so excited about her feat from the night before I couldn't wait to get her out of her footed jammies and put her in something easy to walk in. Would she do it again? Of course, right? She did it last night like she had done it all of her life! Piece of cake.
Nope. Not by 8 AM, not by 10 AM. She takes a nap. Maybe she was tired? Nope. Eats lunch; maybe she was hungry? Nope. Not a single sign that she ever did walk in the first place. She is not even standing up by herself today! She is not even standing alone as much as usual.
Wow.
There is the real shock. I allowed myself to get so excited over her walking, just to see that it was a fluke? I feel ashamed at myself for thinking that this stubborn child would ever actually walk. I should have known better. I shouldn't have thought for a second that those first steps would be anything but short-lived.  Ok, I guess I know somewhere deep inside that Caylen will eventually walk someday. I think/hope? But when, I don't know. One thing I have learned from this child is that you can't count on anything she ever does to ever happen again. So, who knows? I just feel so let down and foolish for actually thinking she would still be walking today.

Is this normal? Is it normal or 'average' for a child to pick something up and forget about it? I just feel so jaded, and like I never want to get excited about anything she ever does again. Sounds horrible, right? But if any of you moms have gone through the same ups and downs with your child that we have, you probably can relate. I just want to know, should I be worried? Or, is this just a stubborn child trait that we just have to overlook?