Often, most developers focus on learning new languages, frameworks, and libraries. However, the most important thing is to understand the fundamentals (which are many) before jumping into new hype technologies. Understanding the time and space complexity of your code, the data structures you're using, and so on is crucial.

In languages like JavaScript, we often find it easy to use HOFs like filter, map, and reduce, and we don't always analyze how these might increase the complexity of our code. Of course, we don't always need to worry about this — in certain situations, we're dealing with small arrays, and using a for loop inside another for doesn't affect the final result. However, when working with large datasets, your approach will make a significant difference and will definitely impact response times and resource consumption.