The first part means "don't worry about the little things." "Don't sweat" means "don't worry." It's just a different way of saying it. For example, maybe you forgot to do your makeup correctly. This is just a "little thing." There are more important things in life to think about. The second part says that "everything is a little thing." This means that everything in life can be perceived as a "little thing." The quote is telling you that life is simple and you don't need to worry about everything.

When you exercise, you sweat. But sometimes people sweat when they are extremely nervous, or frightened. In English there is the expression "don't sweat". Which means "don't worry, everything will be fine". Example... "I have to give a speech at my brother's wedding. I'm so nervous !" "Don't sweat. You'll do a great job." Lucien gives a good explanation about how this applies to your phrase.

It's like - don't worry about little things and since everything are little things, so don't worry about anything

Its mean is that you don't need to sweat little thing, and other way here everything is little thing so it means uh don't need to sweat anymore because here everything is little little thing uh dont need to sweat.