the number three

Have heard a lot about the beauty of the number 3 today, about how some things come in three. and i'll add more here.
1. In primary school compositions, we were told to write 3 paragraphs; intro, body and conclusion.
2. In secondary school, an English teacher taught me that 3 is a good number to remember. Like when you need to include examples, 3 examples will be nice.
For instance, my hobbies include reading, eating and sleeping.
3. In our DIY photo-taking, usually 3 people can be included/ captured in the photo (assuming normal length of the arm).
4. Most of my friends come from a family of 3 children. Maybe it's because we come from the era of the 'Have 3 or more children if you can afford it' policy. See 3?!
5. If memory serves me well, a band/ choir will be expected to perform 3 songs in the SYF judging.
6. I have always taught that 3 mins is just a nice period of time to grant students for a break to the toilet.
Maybe the number three has kind of resonates subconciously in our minds.