I suspect that a character's want and their emotional need must line up in some sense. Say your character want to buy eggs. Can their underlying need really be anything? Love? Acceptance? Validation? Can it be free-standing in relation to the character's history? Can it be free-standing in relation to, say, the cashier in the scene and their wants and emotional needs?
Here's a scene prompt. Alan is at the grocery store. Alan wants to buy eggs and he needs love. The cashier, Kate, wants to be relieved so she can go home and she needs respect. Maybe she was scheduled to leave ten minutes ago but she hasn't been relieved yet.
Does this setup make sense? Can this make sense? A way to answer this: Write the scene, ask if it makes sense, and if not, edit and review until it does.