Don't sweat the small stuff and it's all small stuff

I started to read new book.
It is “Don't sweat the small stuff and it's all small stuff” .
I always have feeling that I have a poor vocabulary.
Actually, I couldn’t understand when I read this title for the first time.
‘I know what meaning "sweat" is. However, don’t sweat? Sweat is verb??’
Then when I looked up “sweat” in the dictionary, I caught on to what title is saying.
It took me five minutes or more by the time it was understood.
I had become tired a little only in it.
Next I started to read body of a book.
But I didn’t know a few words in one sentence.
Every time I came up against a word I didn't know, I looked it up.
I winded up spending a lot of time trying to understand in this first paragraph.
I felt really tired.

Of course, I am trying to read because I want to build a strong vocabulary.
So I am thinking that I will go for “Don't sweat the small stuff and it's all small stuff”.
……
I know! It is not a small stuff!!