Life is CHANGE. Opportunities are endless, limitless, dynamic, and sometimes overwhelming.
A few thoughts on the matter: learn and study multiple options, but make a CHOICE; to do nothing is a wasted moment, a lost opportunity, an unopened door to whatever could be...i.e. a learning/growth experience, a piece to a puzzle, a thread in the grand tapestry of your life and others.
After making the choice and opening that door, PROCEED; follow through. It is a sad, invalid and undocumented case to realize 'it was right in front of me', 'right there', 'so close', 'waiting for me'...tangible, almost.

Also, a 'what if' should be encouraged over an 'if only'. A 'what if' is a curious and healthy expression of desire for growth and knowledge, whereas an 'if only' is wasted energy.
Not to say that we shouldn't learn from past choices or experiences which may have turned out to be mistakes or of a less favorable outcome... but that we revel in the new found knowledge, the stepping stones, the refiner's fire that brings us closer to a defined and chiseled image of who we really are...
where we are, who we want to be, how we should see ourselves, how we should love ourselves, the person we are through evolutionary pressures and choices, opportunities, and everything that leads to the inevitable, change.
Life can be what we make of it, so ACTIVELY ENJOY :)