There is a popular saying in judo which is translated as "Maximum Efficiency, Minimum Effort".

Basically, what it means is that when you try to do a technique, you want to do what is necessary to make it work but not more than that. In other words, be efficient and economical with your actions and effort. That way, you don't waste any time or energy. You do what is needed to get the job done.

In the context of a judo randori, it could mean doing something that has least resistance. There are some students who hate a particular groundwork move. For example, an armlock. Some students do not want to be armlocked under any circumstances. If they had to lose they'd much rather it be a strangle or a hold-down.

If I'm fighting such a player in newaza, why should I go for the armlock, which he is on the lookout for, and which he is defending so strongly against? I might as well go for a pin or a choke, which he is susceptible to because he's preoccupied with defending against the armlock.

On the same token, there are players who absolutely hate being pinned and will do anything to stop a pin from happening. Such players are susceptible to being choked or armlocked because they are too caught up with avoiding the osaekomi.

This principle, of course, applies to tachi-waza too. Some players hate being thrown with seoi-nage. So, they will do everything they can to avoid it, including bending over double. If they do so, they are susceptible to being thrown with sumi-gaeshi. In such a situation, why should I persist with seoi-nage when sumi-gaeshi is readily available?