Nested control structures can really change how fast a program runs, sometimes in ways you might not expect. Here are some important points to think about:

1. Time Complexity: When you have layers of nesting in your code, it can make things slower. For example, if you have two loops inside each other and each loop runs $n$ times, the total time it takes becomes $O(n^2)$. This means as $n$ gets bigger, it can slow down a lot.

2. Debugging Difficulty: If there are too many nested structures, it can make your code hard to read and fix. This can slow you down because finding and fixing bugs takes more time.

3. Readability: When the nesting gets too complex, new programmers might get confused. This can lead to writing code that isn’t efficient, which can hurt performance.

In short, while using nesting in programming can be very useful, it’s important to watch how it affects performance!