Pheobe taught us not to care about others opinions and always be confident in yourself.

Throughout the entire show, Pheobe is always trying new things and trying to be in touch with good spirits. Even though she had a rough childhood and not the best family relationships, she still keeps her head high.

She plays her guitar and sings for Central Perk. No matter how many people tell her she's bad or even listen to her, she thinks she's great so she continues playing.

Chandler taught us that your job title doesn’t define who you are.

In a couple of the episodes, Chandler's job is brought up to ask what he does or what exactly he "is". No one is ever able to guess what Chandler does for a job and it's never revealed.

However, Chandler still buys things for Joey, is able to provide for Monica and their children, able to afford gifts for Christmas and birthdays, etc. It's obvious Chandler cares for his friends and even though they don't know exactly what he does, he still tries to make them happy.

Joey taught us that you don’t have to have great advice just be there for your friends. 

Very seldom did anyone ever go to Joey for advice? However, Joey was always there to listen. Because he and Chandler lived together for most of the show, he got to hear all of Chandler's problems and listened to him. Ross would also vent to Joey just to have someone listen to him.

With all of this being said, Joey was also very trustworthy. When someone went to him and told him something secretive, he kept it to himself. No matter how bad he wanted to say something and have someone listen to him for a change, he kept the privacy of his friends (prime example: Monica and Chandlers affair).

Rachel taught us how to be independent. 

From the first season and then on, Rachel had a job. When she first reunited with Monica she was relying on her father for money to buy things. She then gets a job at Central Perk and starts to realize what it's like to earn your own money and how to live like an adult.

Monica taught us don’t change your future for someone else.

Monica always had dreams and wanted to achieve them on her own. For example, the reason she broke up with Richard. She left Richard because she wanted to have kids and a family, he didn't.

That relationship wasn't matching with her goals so she left. She wanted to be a top chef and she worked her way up to the position she wanted. At the end of the series, Monica got everything she wanted in life.

Ross taught us that if it’s meant to be, it will be. 

Ross always had feelings for Rachel. It all started when they were in high school. Ross's feelings for Rachel never really went away and when she came to live with Monica, they got even stronger. Ross and Rachel were an on and off couple, but at the very end of the series, Rachel has Ross's second child and they fall in love again.