No books told me about this. I figured it out from my two-year old daughter.
Here is the Toddler Peeing Rule:
I ONLY WANT TO PEE WHEN I CAN'T HOLD IT ANY LONGER!
AND WHEN I NEED TO PEE, I NEED TO PEE RIGHT NOW AND RIGHT HERE!
Logically it does make sense, I mean the first part. You only pee when you are urgent. But sometimes situation requires us to pee even though we don't feel the urgency. Like for us adults, before we go into cinema for a two-hour movie, we visit the toilet first; if we are going to take a long bus ride, we visit the toilet first; when you are in the park, you visit the toilet whenever you see one in case there isn't another one later. Right?
But toddlers are so pre-occupied with playing, they think the peeing business is totally a waste of time. Unless they are super urgent, they simply refuse to visit the toilet.
And toddlers make their own rule that nobody can change!
Because of this, we had a few accidents outside the house. She refused to pee when we were going out. I had to let her pee behind the bushes when we were in the park. The husband thought it is so gross. But I'd rather let her pee on the grass than peeing inside her pants.
Peeing inside her pants is ten times worse.
That night when we came back from the park, the moment we stepped out of the lift, she started screaming " I WANT TO PEE! I WANT TO PEE!". I rushed to open our front gate only to see her peeing inside her pants right in front of my eyes - standing - with the pee going right into her shoes. I ended up having to wash not just pants that time.
The other time, I managed to open the door fast enough and grabbed her to the toilet, but while I was pulling down her pants, a stream of warm water spashed right into my hands. I lost the battle by 0.5 second.
And I did not mention the countless times she said "No" when I ask her if she needs to pee before going to bed, only to hear her screaming from her room 15-30 minutes later "Mummy I need to pee!", when I had expected her to have already fallen asleep. I had not started any night training on her yet, so she is actually wearing her diaper, sometimes I feel like saying "You are wearing your diaper, you can just pee inside." but that will make me a really bad mum.
I will say I am already 99% successfully toilet training Kah Yen, which is considered very good since I only started in January, but I am still fighting the 1% because of the toddler peeing rule.