A feeling of...

It seems that as an international kid you always leave things behind, leave things halfway, be it friendships, schools, or leaving things unspoken. I've already switched from IB to the Spanish 'selectividad', leaving this halfway without even changing countries, let alone classrooms and hallways. I feel a complete sense of unaccomplishment with everything I do, and it is my mother that has made me realise this is what's been bugging me about the program change I am facing.
On monday I start.
So now, I've just left behind 1 year of intense work that had so far worked out great, and I'd gotten really good scores on my IB assessments. Yet I chickened out before the end. Is this something I shall be doing all my life?
On the other hand, I didn't really have much of a choice. I was faced with going on with IB, finishing the knowledge I was acquiring through my classes with the teachers I loved, or giving up the dream of doing Medicine. (You see, the IB conversion to Spanish grades is shit, and there is no way possible I'd have gotten into the course with IB, seeing as a 40, a high grade, translates to an 8.6 or less, and also I just couldn't keep up with the extra work I had to do plus the IB assignments). So do I really face no-choice situations in life and just feel guilty about something I had no say in? I just feel that it's always the same cycle, and I've never stopped it. I shall always continue to be afraid of commitment and carrying things out and actually saying (or explicitly feeling) 'I miss you' or 'I will miss you' or 'You're an amazing friend'.
It feels like on that topic I just steer away from emotion and normally face people completely cold-- well, let me clarify. I like listening to people, I like getting to understand them and I think I do this with a variety of people and not for any social motives, but just because I can. On the other hand, I do this without getting attached to them, or most of them, and just see it as a normal moment. When I do get attached to someone, I either fail to realise until it's too late or I fail to say it, no matter how much I try. I want to get out of that fear but so far have not been able to.
As for IB, I guess I really didn't have a choice. There's tons of things I want to do in life, and Medicine is one of them, and it brings me stability and the strength to move on (as one can see with my IB grades). But then why don't I feel satisfied with this answer? Mother's probably right, yet will this spiral ever end?
On the other hand, I can view Medicine as the big picture that I haven't given up on or left behind, and I am looking forward to the lifestyle of selectividad. But I'm still pretty uneasy...