How can a 4 year old already know how to tug heart strings so hard!

This is the conversation that took place after I told my 4yo daughter that it was bedtime last night:

B: Mommy I don't want to sleep in my bed! I want to sleep with you!

ME: Sweety, you'll have sweet dreams in your bed, come on lets go!

B: But when I sleep with you hugging me you're in my dreams!

Heart Tug 1. After this I picked her up and carried her to her bedroom, I set her down beside the bed while I pulled the sheets back.

ME: Ok, B. Lets get tucked in.

B: But mommy! You're breaking my heart.

At this point her crocodile tears started. I bit my lip and tried not to cave in. I lifted up her little body and tucked her gently into bed. I flipped on the nightlight and could see her blue eyes begging not to have to sleep alone. With a kiss gently on her forehead I turned to walk out of the bedroom.

ME: Goodnight B, I love you very much.

B: Kisses don't fix broken hearts, mommy.

She then rolled over and surrendered to the sandman.

It would have been easier to just swoop her up and cuddle her to sleep in my big lonely king size bed. It would have been so easy just to rock my baby back and forth in my arms until she was drooling down my shoulder. Instead, last night, I drank a beer and congratulated myself for sticking to my guns.

**Edit for clarification: This is the equivalent to a temper tantrum for her. She says these kinds of things any time she's not getting what she wants. So me caving to this, would be like you picking up your toddler every time he/she squeaked. It's exhausting for you, and it doesn't achieve anything besides stopping the squawking. Or in my case, the heart breaking words. She knows how to hit my soft spot. If I continue to cave every time she takes a low blow, she'll learn that it's okay.