The advantage of having an overriding purpose and/or activity is that the rest of your life is not random. A multitude of other activities, washing the dishes, changing auto insurance, recycling an old vacuum cleaner, going through the closet, and on and on, all play a part in this purpose. Otherwise they are just an endless array of chores and 'have to's' that whittle away your energies until you are drained. You are doing this or that for your bigger purpose.
The disadvantage of being purpose driven is that you can't go with the flow so easily. The structure of your life has this direction and you can't alter directions too much. An adventure, or trip, or just a spontaneous pleasure can throw you off course. There are so many variables to keeping your life afloat that voluntarily choosing distractions can overload you. Your routine gets shaken. As said there are already enough interruptions that make it hard enough to be focused.
If you had or were given enough strength from the start and power you can absorb taking different roads and different activities and still rebound and come back to your purpose. If you don't have any fat in your makeup your lee way is limited and you can't afford to be thrown off course too often. Your recovery time makes this a liability.
So these are things to consider for being purpose driven.