And not that you are careless in applying the stamp.

Along with Latvian stamps I've also collected postcards and covers. Over the years I've noticed stamps applied in various positions particularly to postcards but have never given it any thought. At least not until the last few months. I belong to a closed group on Facebook and had been posting some of the postcards showing both picture and postmarked side. A fellow collector posted the item below.
As you can see the direction and also whether right side up or upside down connotes a particular message. Whether that was something done in the corner of Russia that Latvia occupied or was done in other areas and other countries, I don't know. The English translation in red was added, both because reading the German script is hard and also not everyone on the site speaks Latvian. Below are 5 more examples from my collection. From what I can see it seems to have died down after WW 1.

I think of you all the time.

I think of you all the time.

Yes.

I can't live without you.

Do you think of me?