This is one of three seals of my calligraphy brush & ink painting, located on the lower right corner. The characters are in red letters believed to be Chinese. I believe that it could possibly be the name of the artist.
This is not a name seal but something called 闲章. 闲章 is a non-name seal. Usually, the content in it is good words or good wishes. In your case, “修身养性” is a pursuit of Confucianism. It means strengthening yourself, as the first step of “First free yourself of wrong-doings and evil thoughts, then bring order to your family, after which govern your people well and the land is your”