The Christian's Secret to a Happy Life, by Hannah Whitehall Smith.
From Christian Classics website: Sometimes it just feels like life is beating us up. We worry about our family, our health, our money, our time, and in the process we run ourselves ragged. These stressors are not a recent phenomenon, but have been with humanity since the fall. Even though The Christian’s Secret to a Happy Life is over 130 years old, author Hannah Whitehall Smith was aware of the age-old problems that plague humanity.
In her studies, she discovered that there is a way to handle the stressors in our life in a healthy way that builds us up instead of tearing us down. That way of dealing with life’s trials is through living faithfully in the rest and comfort that Jesus offers us. True happiness does not come from an absence of difficulty, but through the loving embrace of our Savior.