Its important to know the difference
Quite often when we are venturing in something new, we are faced with doubts, fears. We are even tempted to give up saying, it was impossible. At this time if we can draw the line between the impossible and the unknown, then we can quite easily transcend the fear.
More often than not, the task is only unknown. At such time, we need to list down things to do, and find the best person/resource to guide. And slowly what was impossible starts becoming a reality.
On the other hand if it really is impossible, still try. At least now we know that its impossible in this way. Perhaps it’ll be possible some other way.