Well the problem with your analogy is that in real life people cannot control their location in time. We are constantly moving into the future at a steady rate. This forces us to make decisions which necessarily forecloses pursuing all opportunities.

The big problem is that they gave the Doctor complete control over the TARDIS. In the classic series, the Doctor's inability to control the TARDIS gave the writers a narrative justification for explaining why a companion could leave and not be seen again. In the new series some kind of tragedy is generally necessary…