Stay on Track
It's a phrase we hear all the time, meaning, don't deviate from your chosen path - but it is, in fact, nonsense.
The phrase derives directly from navigation, specifically airplane navigation. There one sets a course (the intended direction) but because of winds and weather the way one actually flies is often rather different. This results in one creating one's 'track' - where one has in fact gone while trying to get directly from A to B.
It follows, then, that one can never fail to be 'on track' because that's the route one's taken. One can be 'on course' -- if you're lucky.
The original difference between the words conveys an important life lesson; we may plan a course that is theoretically perfect, but life will always mess with any such plans. That's when we create our track.