Is this even possible?

Possibility, potential, prospects...is there anything more exciting? Or terrifying? I've been thinking about possibilities and opportunities lately, and how, recently, things just haven't "worked out" as I thought they were going to. Perhaps I focus on the plans that fall through more often than the plans that come to fruition, but it seems to me that in the past few years, most of my plans have gone awry. The best laid plans of mice and men... or so they say.
It's frustrating though. Sometimes events beyond my control come into play, and a lot of times it's just easier to lay down arms and say, "Oh well." I find this happening often when I decide something like "I'm really going to start exercising, every day." I'll make a plan, a schedule, and put myself in the mindset that "this is really going to happen." Then something will happen, like I'll come down with a sickness, or it will snow, or I'll have to alter my ideas in another way to accommodate this new situation. And it's easier to just say, "Meh, there goes that idea." However, part of me thinks that when this happens, it's my resolve being tested. I'm being asked from God or the Universe if I really have the discipline necessary to undertake whatever plan I have concocted. And I just fail this test every time.
But that can't be a way to live. I've gotten so used to things interrupting my "best laid plans," that I'm expecting it now. Motivation is becoming a real problem as a result of this. Normally, I'm one who is so competitive and fierce that if something comes along to throw a wrench in my plans, I'll find another way around it. When I was in college, I decided I wanted to follow a degree program I had found at another university. When it turned out my university didn't offer that particular degree program, I made it myself, followed it, and now hold that degree. I was not able to go on exchange to France during my junior year of college because I was supposed to leave on September 11... and while I am very fortunate that all that day did to me was temporarily delay my exchange trip to France, it was still a plan that failed.  And even after being told that I was not going to be allowed to go at all the following semester, because of "program issues," I fought and went anyway. I used to be good at overcoming obstacles in my path in order to fulfill my plans.
But recently, I have become less and less adept at this. Even something as simple as exercising every day can be ruined by something as trivial as a cold. And now, I am being presented with something that has the potential to be a great opportunity. And I am so tempted to be lured into the idea that this could be a real possibility. Because it would work so well; it would align so well with the "grand plan" I have set forth for myself. And even though I am excited about it, and crossing all my fingers that it could work out for me, I'm hesitant. I'm stuck thinking, "Is this even possible?"