Why does my character do these things? Raid, grind, etc? What is he striving toward? What is his purpose?
It's not about him. It's about you.
Do you have any purpose to play the game? And about the first question... your character does these things because you tell him to.

Pal, even if you are Gifthorse, or UserF*CKINGBILLIONS I don't care that much. Just to tell you that the purpose of the game is not to reach 50. It's not to complete contents first before everyone. It's not to strive for loot. It's not even being one of the best players in the world.
The sole purpose of the game is to have FUN. Go around, take a party and create your objectives, your achievements! For example, do a Thousand Maws or Dzemael Darkhold in Swimsuit, complete the R45 dungeon with less possible minutes of spare time, Chain # monsters of your same level,...

Dude (because User201BILLION is too long), you can still have Fun, but you have to get out of this "Why am I doing this" nonsense.