I am the kind of person who will invest personal time to develop my career - I will read up about stuff in my own time, make and nurture connections using my social media accounts, network with peers, prospects and potential employers in my own time. Because if done well, this can all make me better at my job, get me a better position, and generally help me advance my career and make me land better-paid roles.
I have done well for myself, and I am convinced that the above has helped. But I know a few people who will not invest any 'personal' time doing the things I mentioned above, because, well, it's their personal time. But then complain because they don't move up the ladder (quickly) or don't get the better-paid roles.
I'd be very interested to hear your thoughts.