How to understand the title in one step: Read.

Learning is the acquisition of new information. There are 2 categories of new information: Applied and Unapplied. Unapplied information is generally informative: What is electricity? How do planes fly? Unapplied information can give us useful context about the world or about certain ideas, but it doesn't affect your life in a meaningful way.

Applied information however, directly affects your life. Brushing your teeth prevents tooth decay. After learning this you brush your teeth routinely. Money loses value due to inflation. After learning this you start to invest regularly.

When we learn applied information, our behavior may change naturally. When our behavior changes, our old self dies as a consequence. The old self was uneducated, inefficient, or maybe even counterproductive. The old self was living a sub-par life.

Unfortunately, we cannot rely on the natural process of learning to correctly categorize new information. The old self can be resistant. The old self is complacent by default.

You must pay careful attention to new information you're learning. It will be miscategorized at times. New information: Women desire confident men. Did you say hello to the cute girl that walked by? No. The new information didn't change our behavior - was it miscategorized? Perhaps the old self is being resistant.

The solution? Kill yourself. Manually move the knowledge to the Applied category. It will be uncomfortable, but the natural learning process didn't solicit a change in behavior. The old self wasn't living a life worth living.

Accept that the old self will miscategorize new information. Accept that there is life after death. With patience and dedication, you will become a skilled assissin and old self will die many graceful deaths by your own will.