Conservatism attempts to discern a "pattern in history" that will yield "clues" as to what is feasible or unfeasible.
When you have a reasonable amount of knowledge of history, you notice that the past is not past. That it created the present and that patterns repeat themselves. Nothing is exact, that is why you must look for patterns. War and peace for example, are two sides of the same coin, when someone promises us they can deliver world peace we know from our study of history that they do not have that power, no one does. When someone tells us they can make everyone rich, or poor or equal we know from our study of history that it never works. When someone promises that they can bring unending economic growth we know that they cannot. No matter how honest or good they are, it is more than all of mankind can achieve.
We should be looking to achieve small goals, ones that can be measured and stopped if they are wrong-headed. We should remember that "there is nothing new under the sun", it has probably been tried before and the reason we don't remember it is because it failed. Not all of our efforts will fail, but a proper understanding of history will help us to work out what has worked and what has not worked. What is worth our efforts and what we should not bother ourselves with.
This principle is one of 5 that Francis Graham Wilson proposed, for more on this important Conservative thinker:
Upon Hope Blog - A Traditional Conservative Future