Apply Custom Pathfinding Goals to EntityPlayer

Hello again!

I'm trying to make an NPC that can move towards the player and away from the player if its heath is lower than for example, 3 hearts. How could I possibly implement this into my project?

If this helps, I used this video for the NPCs.


If you can, please provide some example code for me to use because I'm not very fluent in this field of programming yet.

Thanks!