What does a promise mean?

I have been putting it off for months longer than I should have.  Our three year old privilege is to move to a big bed.  Bobby is approaching three and a half and was still totally content to be in his crib and rocked like a baby every night.  What's the rush?  After all, there's no one waiting on his crib this time.  Nobody to push that little bird from his nest!   So I reluctantly started the conversation with him about the end game of moving to a big boy bed, but first we could take out some of the rails in his crib to make sure he was ready.  What I didn't say (out loud) was, "Those can be put right back in, if it's a huge mistake."  He talked about it with me, but didn't seem particularly interested in it at the time.

We had three nights in a row where he wet the bed.  He's been dry for months and out of night time diapers.  I had the sheets still off when naptime came around and so just started putting him in Isaac's bed for naptime.  He was fine with that and was still going right to sleep and staying put.  After three days of that I asked him, as we were walking up the stairs for bedtime, if he wanted me to just take the rails off his crib tonight since he had been sleeping in a big boy bed at naptime.  His response was so very precious.  His face lit up, and he exclaimed, "Tonight?  Yes, oh yes!"

I reminded him that he had to stay in his bed though and followed it up with, "Promise to stay in your bed?"

He said still very excitedly, "Yes, I pwomise!  Pwomise means you weally will."  Gotta love those w's replacing the r's!

Melt my heart.  I don't even know where he learned that definition, but I love it.

He is doing great and never ever gets out of bed without Isaac or I telling him it's okay.  He loves to remind me that he can get out of bed all by himself.