While change is often good and neccesary in life, the Torah prohibits other types of change. For example, the Torah explicitly forbids השגת גבול -- adjusting and overstepping boundaries in the Land of Israel. Put simply, I can't change the markings on the border between my fields and my neighbor's so that I get more while he gets less. Rashi explains that while moving the border of my house to overstep my neighbor's is indeed also stealing, God gives an additional admonition in this particular area. Why would the Torah need to prohibit a behavior that it already forbids?
Ramban notes that a person might come to feel that God had apportioned the Land of Israel unfairly for any number of reasons: the land tracts seem uneven; my needs are greater than my neighbor's -- or any number of other reasons. When I arrive at this type of conclusion I don't feel consider moving boundaries "stealing." Rather, I'm just setting things straight.
For this reason, the Torah adds the additional prohibition of "changing borders." God knows what he's doing. He gives every person the proper piece of the Land of Israel -- despite the fact that we may feel slighted. So even though I might feel justified, I still may not take what is not mine.
In other words, when we approach the notion of change during the month of Elul, instead of looking to change what we've been given, first we need to change ourselves. That's the best place to start.