Why your protagonist's longing should lead to their fear
What your protagonist longs for is what they'd have if their deepest fear didn't run them, so chasing it should walk them into that fear, or the longing is decoration.
Want vs. need in a story: how to write both
What your protagonist wants is the goal they chase on the page: the job, the person, the win. What they need is the change in who they are that would actually get them the life they long for.
The two pull against each other for most of the story. A false belief keeps your protagonist chasing the goal, a fear keeps the need out of sight, and the turn usually comes as one costly choice that can look like losing from the outside.
This is the heart of a character arc, and the insights below take it one piece at a time.
Every insight on this topic
The selfish version of the goal your protagonist gives up
Nearly every goal carries a selfish version, how your protagonist would get it if nobody else counted, and that version is what the turn asks them to give up.
How a character's need surfaces over the story
What your protagonist needs moves from something they'd deny, to flickers they push back down, to something undeniable once their false belief breaks, and that movement is the arc.
When your protagonist wins without changing
If your protagonist wins the goal without changing and the story treats it as a triumph, the story has adopted their false belief.