You can always tell the difference between want and need if you are able to make a couple of observations. It applies to nearly everything.
When something needs to be done, one is likely to do the bare minimum. When it’s what you’ve wanted, there’s no limit to the distances you’re willing to go.
And when one is needed somewhere, perhaps being near a loved one, few people go above and beyond in providing the other party with what they need. Even if they do, there’s still a chance that it’ll be done out of resentment or be used as a way to take revenge.