What is the most practical and easily applied lesson you learned?

Pages: 1

powerpoint slides:

Spacing: Double spaced

Topic:

Details: Review and reflect on what you learned in the past 8 weeks. What is the most practical and easily applied lesson you learned? What was the hardest to grasp? Why?

I use this book for the class. You can use this book to answer this question. It has to between 75-150 words:
Pratt, P. and M. Last. (2015). Concepts of Database Management, 8th ed. Boston: Cengage