The phrase "hard worker" refers to someone who puts in a lot of effort and works diligently or with great perseverance, usually towards achieving a goal or completing a task. Full definition
I am a very hard worker with a strong dedication to maintaining excellent care to our patients, clients and staff. (arguellopet.com)
Also a very hard worker with the drive to succeed. (livecareer.com)
They have made me deeply respectful of hard workers regardless of their jobs and more aware of the sophisticated craft knowledge required to make seemingly simple things happen. (gse.harvard.edu)