I certainly don't view my education and future career as a dreaded chore. However, while I was in undergrad, my advisors STRONGLY urged me to slow down for various reasons. I grudgingly let one of them talk me into going to Europe and then taking time off. At the time I was unsure if I should have been doing it but, looking back, I realize that it was the right thing for me to do.
No one is saying that aspirations and enjoying life are mutually exclusive. What people are getting at is that often students myopically focus on their aspirations and forgo the chance for exploration and enrichment outside of their studies. A few of my friends here in dental school rushed through undergrad, one them is doing a seven year program, and are now discovering that they really would have benefited from either time off, taking courses in literature, business, and so on, traveling, and the like. They still like dentistry but they also are a bit sad about this. Why don't they just do all this after graduation? Well, as a professional and an adult there are certain obligations and responsibilities that make opening certain doors that were once available but are now closed. Re-payment of loans, spouse and family obligations, mortgages, car payments, insurance, not to mention your practise - which is a business and just doesn't run itself - are just a few of the many ways in which a life can get very complicated very quickly. Aspirations are a good thing - I certainly wouldn't be where I am today without them - but as someone that has taken time off from school, who has worked in the 'real' world prior to dental school and who is older than the average dental student I think it is good advice to tell younger students that it's important for them to take advantage of where they are right now and to enjoy themselves because the circumstances they are in now will never be the same later on.