Advice if you're writing to your kids

As soon as I found out I was going to be a dad I started a blog of letters to my kids. The posts started out, "Hey kid,..." Of course, they quickly changed to, "Hey kids,..."

I've tried to be very intentional with what I write to them. I want my kids to feel like they were loved when they read these letters. I don't want them to feel like they were just a screw-up.

There are a few principles I try to apply to everything I write to them. Some of these principles are based on my thoughts on things my parents wrote to me. Others I guess I'm just picking up as I go.

1. Tell my kids I love them.
2. Tell my kids WHY I love them.
3. Give my kids tangible examples of things they do that make me proud of them.
4. Don't tell my kids shameful childhood stories about themselves. They don't want to remember their foolishness anymore than I want to remember mine.
5. Try not to compare my kids to one another, at least not in terms of "better/worse."
6. Don't write everyday. My kids likely won't read these until at least 18 years of posts have been written. They don't need to read every single detail.
7. Write at least once a month, even if my creative/reflective juices aren't flowing. It's not helpful for them to have gaps left in their story.
8. Tell them about the friends in your and their life. Experience says these relationships will likely change and evolve. It's fun to look back and remember them as they were.
9. Speak to each child directly. I often start my posts with, "Hey kids," but try to make a point of speaking to them individually. They're individuals, not just twins.
10. Never say too much in one post. Rambling is annoying to read.

How about you? What sort of principles have you tried to apply with writing to your kid(s)? If you don't write, why not?