Why abstract ideas slip away
Some ideas are hard to hold because there is nothing to picture. Words like "inflation", "irony", or "opportunity cost" can sound clear when you read them and then vanish an hour later. A concrete example gives the idea a shape. It ties the general rule to something you can see, hear, or imagine.
Take opportunity cost, which means what you give up when you choose one option over another. On its own, that is easy to forget. Now picture it: if you spend Saturday at a friend's party, the cost includes the extra shift you could have worked. Suddenly the idea has a face.
Use more than one example
One example helps, but it can also trick you. If your only example of a mammal is a dog, you might think fur and four legs are what make a mammal. Add a whale and a bat, and you start to see the real shared features.
So look for several examples that look different on the surface but share the same idea underneath. Then ask what they have in common. That common thread is the thing you are really trying to learn.
Make your own
Textbook examples are a good start. Making your own is even better, because you have to understand the idea to build one. Try examples from your own life: your job, your home, your hobbies.
Be careful, though. A made-up example can look right and still miss the point. Check it against a definition or ask someone who knows the topic. If you cannot come up with any example at all, that is a useful sign that you need to review the idea.
Worked examples for problems
For skills like math, coding, or filling in a tax form, worked examples are very helpful when you are new. A worked example is a problem with every step of the solution shown. Study each step and ask why it was done.
A good pattern is to study a worked example, then try a similar problem yourself without looking. As you get better, lean less on the worked steps and solve more on your own.
Try it
Pick one abstract idea from something you are learning. Write down three examples of it from very different parts of life. Then write one sentence saying what all three have in common, and check that sentence against your notes or book.