"呆板单调的生活" can be translated into English as "a dull and monotonous life" or "a rigid and unvaried life".
"Dull and monotonous" emphasizes the lack of excitement, variety, or interest in the life.
"Rigid and unvaried" highlights the inflexibility and lack of change or diversity.
Both expressions convey the idea of a life that is uninteresting, repetitive, and lacking in stimulation.