I watched [an interesting YouTube video about commas](https://www.youtube.com/watch?v=GHnl1O3NGJk). In this clip, the author says commas are needed with FANBOYS (for/and/nor/but/or/yet/so). 

The example is as follows:

> 
> Bartheleme was accepted into the University of Chicago, and he is on the waitlist for Stanford. 
> 
> 
> 

However, [in this YouTube video clip](https://www.youtube.com/watch?v=pOwcovqtkGY), the author says it is not necessary when the subject in the first clause is different from the second clause. 

The comma-less example that the author uses is:

> 
> They went to get pizza but the store was closed.
> 
> 
> 

The example that uses a comma is (the comma is needed as the subject is the same for both of the clauses):

> 
> They went to get pizza, but came back with ice cream. 
> 
> 
> 

It's confusing because from the first YouTube clip the FANBOYS always need commas, but from the second clip we need the comma only when the subject is the same. 

[In this video clip](https://www.youtube.com/watch?v=ZV81aqY2Jys), there should be no comma with:

> 
> She started the car and drove down the hill. 
> 
> 
> 

This example is quite contrary to the second one. 

What is the correct usage of comma with FANBOYS? For example, do I need comma or not in this sentence?

> 
> I have raised him and tried to give all the support that he needed to become a person who leads a fruitful life,(?) and a model citizen who contributes to make the world a better place.
> 
> 
>