Every once in a while, at least in the parks that I find myself in, I'll see a smile on the face of somebody running. They're enjoying their workout. That's not to say that running has simply become easy for them and thus enjoyable, but it's clear by their expression that the running is not a horrible experience, despite the pain and fatigue. This is optimism, focus, and purpose in a nutshell: even the toughest physical feats become possible because of their attitude. More commonly, I see the person whose facial expression says that they desperately need medical attention, despite their body soldiering through the workout. (As it should.) They look like they hate running and struggle to justify their suffering: to which I say, why are you running in the first place?
It's a clear difference. The first runner, whose face shows optimism and determination, is running with a sense of purpose. It's easy to justify why they're running: they do it for the runner's high, or because they have a season to prepare for, or they just love running for running's sake. They got up and put on the running shoes with joy. With purpose. A goal.
The latter, however, had to force themselves out of bed in the morning and get ready to workout. Today's workout was not a mission that must be completed, but an obligation. A horrible, burdensome, unenjoyable requirement. That's no purpose, in fact often times it is a fear. Usually, the fear that if I don't get up and run, I will gain weight again.
The difference between goals and fears appears in nearly every walk of life: there are 15-18 year olds deciding to become lawyers and doctors because they are scared of not enjoying the luxuries that they grew up with. Students get home every single night and study for hours on end, not because they enjoy learning, but because they are scared of an uncertain future in which they aren't accepted into a top-tier university.
The fears that may at one point drive you to do something positive will not, and should not persist. The fact is that most fears are irrational and can (and again, should) be overcome. The fear that you will gain weight should not drive you to run, but the goal of improving your health. Your medical school aspirations should be driven by a goal to help others, not because of fear of societal judgment. Study for the sake of becoming more intelligent and capable, not because you cannot handle uncertainty or change.
Don't have fears. Have goals, and pursue them with a smile on your face.