This is a perfect example, A physical act , a split second decision that is easy to relate but what of the conscious decision that is based on hours of agonizing over doing the "right" thing as Cutten offered in his post and the person chooses to risk everything by continuing to act in disregard for their own self with obvious detriment to their future life but for a cause, soemthing that is not a physical act I had started a thread on this very subject here but not as clear as your (Cutten) post, trying to collect my thoughts. Events seemed to line up where I, with the most experince and the clarity, could see the obvious failed outcome. I weighed the personal consequences of my continued actions and basically backed off. I didn't create the problem but in the end, lack of my action is a personal failure (following through) in my book, people may sympathize and nod with understanding, but... oh well... I went to the edge......others were depending on me....and assorted excuses.
That's more philosophical/epistemological terrain and , I think, ultimately goes back to the nature/nurture and blank slate questions. Either way, people do act out of best interest, either short term or long term. One decision can be in short term best interest, but antithecal to long term best interest. Another could be vice versa. Either decision is in best interest, it's the time horizon of decision making which is in question, not whether or not one acts in their best interest.
There are plenty of examples if selfishness. Harry Connick Jr. was photographed keeping an African-American above the flood waters resulting from Hurricane Katrina. Caroline Kennedy said Obama reminded her of her father's greatness. Later, she was almost made an ambassador. Madonna's adoption of a boy from Africa is totally selfish. Out of control Democrat spending, which mortgages our children's future, is selfishness. etc, etc
You are moving past decisions based on the physical into the realm of the metaphysical with that question. One perspective is "Life is school", and if we do not learn a particular lesson in one lifetime, we return of our own volition to try again. Hence the decision made "by ourselves", though it would be a "higher self" that ourselves in the here and now have temporarily forgotten.