Your life usually changes pretty drastically every five years or so. Think of it as Moore's law for humans. While Moore's law reckons our chips get faster by two fold every three years, it is not to be taken as some irrefutable formula per se but rather as a trend that's held very well for decades. Likewise most will find their lives to have taken a considerable turn if they take stock every five years. That's because many changes happen in half a decade: you lose loved ones to the afterlife; make, renew or break romantic connections; change jobs or careers and even change residence. Any combination of the above will spell great change.
Five years ago did you accurately envisage yourself to be exactly where you are now? Think romantically, financially, spritually, health-wise, home-wise. I'm going to boldly say your answer is no. Life is too dynamic by nature. Opportunities, setbacks and twists occur that you cannot account for. Unpredictability (not of an unmanageable, chaotic variety though) is hardwired into life. If something is completely predictable it becomes boring, so be grateful that you can't tell the future.
Excessive goal setting
Why then are many people still so infatuated with trying to know and control what fate has in store for them? Excessive planning and goal setting is reflective of this. Nevermind meeting the end-goal, we become pedantic about the way in which it must be met e.g. Go to Oxford, complete a degree, meet beautiful, intelligent brunette, join Goldman Sachs, manage a hedge fund, make a hundred million in three years, marry, move to the Cayman Islands...
If somewhere along this chain of plans and expectations there's a deviation, what then? If Oxford doesn't accept you, if you get into a medium sized firm instead of Goldman or you don't make that hundred million in three years, is life then failing you?
Stop obsessing over the detail and just keep going
Set objectives and draft a plan to meet them. Work every day and focus on implementing the plan, not on meeting the objective. Be open to turns and curve balls that come your way and adjust your course (albeit without compromising on your overall vision). If you get into a public college instead of Oxford, make it work. If you don't make a hundred million within three years, adjust your time frame to five years and forge on. The important bit is to maximise each day and not be obsessed with how your objective is going to be met or even when it will be met. You have plans, you have deadlines, but sometimes they can't be met in spite of your best efforts. All you can do is work with the resources at your disposal and maximise each day. The rest, as a matter of fact, is out of your control. Life is a mixture of planning and surrender.
One unexpected event that isn't to your liking can form the seed for something else. I had to stay at university one year longer than planned, and in that year I met the woman I now refer to as my fiance.
You don't need to know the journey from A to Z. The journey wouldn't be worth it if you did. Jack Canfield, father of the Chicken Soup series of books, remarked that you only need your car's headlights to illuminate the next few metres in front of you, and you can drive all the way across the country at night in this fashion. When the road curves, you turn your steering wheel, if a steep hill approaches, you change gear. There's nothing you won't be able to handle and there's no need to know the entire route in advance. With our lives it's no different.