This again is not a black or white question, because it really depends on what the work is. The value of the work depends so much whether your occupation really has value. So again, if you have a job where you actually think it's not that valuable compared to something else, than you are probably right. For example, we knew one student had a job, doing computer software, designing a program. That sounds fine, and we need people to design computer software. However the particular job that he was working on was to make certain software that helped a movie company make a silly science fiction movie.
That's not as fulfilling as making a computer program that would help the Red Cross design their facilities a bit better and create more efficiency within the organization. Both people are computer experts, but one person is just doing a job that helps Hollywood people make more money, selling a silly movie, the other person does a similar job but it helps the Red Cross, which of course, is one of the best organizations in the world for helping people.
So depending on what the job is for, you're going to see whether it has value or not. Now as to the right amount of effort that you put into it, this is going to be very dependent on your other activities. Anyone who is single can put in more time for work. When you are married you can't put in as much time because you have to give some time to your partner. Once you have kids, again, you have to lessen the amount of time at work, because you have to give time to your kids. So the amount of time available for work is very dependent on how much time you have to give to other people.