how does one decide

how does one decide if the positives actually do out weigh the negatives to one certain situation? like if the far fetched idea would actually but a feezable idea... or that if you took one huge leap of faith that you wouldn't be completely crushed ifyou gave everything up to find that your plan would go completely sour... and how would one go about picking up those pieces... why must these difficult decisions always seem to make it easier to stay in the same rut that you have always been in?