In my experience, giving your all to a job usually means going above and beyond the boundaries of your job and nobody, neither bosses nor coworkers like that.
Most places want automatons who learn the ropes and hang tightly onto them. Fifty percent is about right for your job and for your well-being.That doesn't mean you do a half-assed job. It just means that you give your job the importance it deserves.
Work to live and don't live to work. Toe the line, but don't stretch it tight.