A word on planning

As an individual who hates who doesn't like being caught off guard, I often wonder about the concept of planning. Personally, I like my 5 year plans. I like knowing that 5 years down the line, I am in a spot that has been planned for earlier and the consequences of everything can be dealt with. Now I have been criticized on two fronts for that. One: My time horizon is too long, a lot could happen between tomorrow and 5 years from now. Two: as sort of a corollary to that, this horizon and this fixed mind frame makes me inflexible.
It is true that many things can change in a 5 year time frame that can offset, nay overthrow, plans. But, to tie in both fronts of the aforementioned argument, I think that planning for various scenarios whether it is a 5 year time frame or a one day period, is arguable the best... methodology... from a personal front. Someone whom I know decides not to plan in that much detail since it's better to live by the minute to allow for flexibility. On the other hand, another person I know likes to plan everything down to every tiny detail because this eliminates uncertainty. By combining these two methods and taking the time out to perform a scenario planning exercise for the next 5 years, you keep the cards of uncertainty at bay, while allowing for the twists and turns of life to be accommodated.
Ofcourse, not all scenarios can be planned for. And perhaps, this is where the biggest flaw lies. But it's the middle ground between absolute flexibility and absolute certainty, as mentioned in the two scenarios above. But, at the end of it all, no matter what your planning style is, isn't it better to pick the option, or a course of action, that will allow you to eliminate uncertainty for as much as foreseeable while providing favorable consequences?
For example, let me provide you details to what I am referring to. A good friend of mine had a chance to go to singapore to study at a prestigious university for his high school years (Grade 9 through 12) on a full scholarship. Upon graduation, he would be provided with excellent odds of getting into Harvard University, USA (and Harvard alone) to continue his undergraduate career. I say odds, since it is dependent on his performance. While his performance did not have to be spectacular, it needed to be good. And mind you, he is capable of spectacular performance. However, the offer to study in Singapore was declined since it meant a charted course for the next 6-8 years and did not allow for flexibility. Is he too young? What if he decided to not study in the USA? What if he did not like Singapore? What if the culture at Harvard did not suit him and he would like to transfer out? Ofcourse these are only some of the questions floating around in his mind as he made this decision.
My answer to this scenario is simple: look at the bigger 10 year picture, suck it up and work hard. The quality of education, the level of possible maturity to be achieved, the brand name of one of the best colleges in the world, all outweigh any of the possible questions he could have had. And it is this planning I am referring to. Plan for many scenarios, but pick one scenario that offers the most benefit versus the risk at the expense of 'flexibility' and proceed. To have rejected this offer is in my mind short sighted and possibly (albeit hopefully not) a career limiting move at the age of 14.
One of the goals in life is to eliminate risk and allow for as much benefit as possible by picking the right charted plan. Right?