It’s easier to dam a stream 

than to hold back a river.

Think of a huge river: say, the Amazon, Yangtze, or Mississippi. 

Now, let’s say that we are told that, in order to reduce flooding, we have to dam that river. And so, logically, we head upstream, looking for places where the river is narrower and more manageable.

Similarly, if we are to gain some control over our habitual behavior—from that which wastes our time or impacts our health to that which inconveniences others or, even worse, distresses them—we would look for the minor habits that contribute to such overall bad behavior. 

The habits that are not yet well-established would be the easiest to control. These would be the easiest to “dam up” before they become unchangeable and firmly anchored.

In time, as we become more skilled at stopping these fledgling habits, the more equipped we will be to tackle those that are more entrenched.