what they probably mean is you are to emotionally involved in your work. This isn't including things like being passionate or proactive about your job, just things like you let what people say get you anxious or upset or you put too much pressure on yourself to get things done on deadlines and to a certain standard, possibly to the point that it's crossing over into your personal life and is plaguing your mind outside of work.
If you feel happy doing the extra work and it's not really effecting you then just ignore what people say, however if you feel you need to put in extra time just because you have to get things done and it's chipping away at your leisure time then have a talk with your manager to discuss other options. If you are doing more hours to get work done and you haven't made the company aware of it, they will just keep giving you the same workload because you seem to be handling it, don't be afraid to speak up. The company needs to change things to suit your standard hours, you shouldn't change your hours to meet the deadlines.