Is Buddhism "opposed" to striving, or working towards a goal that you really want

I've found that it is pleasant and exciting to work towards a goal, for example: wanting to run a 21km race, imagining the crowds, imagining the personal accomplishment. This requires a certain amount of dissatisfaction with your current situation (I can only run 5km, I need to train more). However, what I understand from Buddhism is that this attachment to an end result in the future causes suffering. Does one live with some attachment and accept it, or is it something to be avoided entirely?