There's No Perfect Post
Don't spend all of your time trying to create the perfect post. You won't be able to predict how many followers will react to your posts. All you can do is be honest in your thoughts and opinions. Once you do that there's a good chance that it will relate to a couple of your followers.
Let's say you have 1,000 followers and 10% (100) of them react to your post. Do you consider that to be a success? I do... You don't know what that 10% may do with your post. They may share it with their friends or they may use the information to create something. Trust that the content had some value, that's why they engaged with it.
If you have a newsletter it's a little more difficult to try and not be perfect. Since there's not really a way to measure if your newsletter is working you just have to trust. Followers subscribe to a newsletter because there's something they are getting from it. Just know if you have subscribers you are doing something right.
An example is this newsletter you are currently reading. I don't have any idea if you are getting anything from it. I hope that you are... Eventually, as you read the techniques and implement them into your daily work you'll at some point come back and communicate with me in some way. This could be in a week, a month, or even a year from now.
Don't spend all of your time trying to measure; use your time writing content to help your followers. The more you write the more interaction you will get. You will then start to get a feel for what is happening in your social communities.