Had to convert the 12cm to inches so I could get a better understanding of the heel height. Somewhere around 4.75". Usually, my limit is right around 4" for reasonable comfort and good walking ability in my stiletto boots. Sure, I can "walk" in higher heels, but not very well, or for very long, without discomfort.
So much depends on the design/engineering of the heel/boot/sole. I am so thrilled to have found some nine west stiletto ankle boots with heels somewhere between the 4.75-5" range that are relatively comfortable. More importantly, I can walk in them fairly confidently with minimal discomfort.
Your boots look great, and I surely understand how great it feels to be able to wear/walk confidently in them! Wearing them to work on a day when you would be alone in the office was a smart plan indeed.
I find that much of my "timidness" in my various stiletto booties/boots is caused by being concerned about wrecking the heels prematurely while out and about. I have spoiled a few heels on my favorite pairs which was very upsetting. So, I think I tend to "walk gently" in my boots, without even thinking about it, in an attempt to avoid ruining them. I'm thinking this works against progress in the long run though.
On a positive note, was wearing my 3.5" block heeled ankle boots in Home Depot yesterday, these boots are great for everyday chores, shopping, etc. Super easy to walk in, without the worry of damaging stiletto heels. Was trying to navigate the damn self check out, god forbid you try to pay with cash! A very nice younger attendant came by to help then complimented my boots. I spent a minute or so chatting with him and thanking him for taking the time to compliment me.