There are four stages of motivation, says Benjamin Hardy in an article on Medium.
That may be an oversimplification, but a useful one when creating characters for your screenplay or novel--as well as for a bit of navel-gazing. Here's how he defines the four stages:
At stage two, you are motivated by reward. Everything you do is to get what you want.
At stage three, you are motivated by duty. You’re going to do what you believe you should whether you receive a reward or not.
At stage four, you are motivated by love. You have moved beyond worry for your own needs."
THE UPSIDE AND DOWNSIDE OF EACH STAGE
Naturally, each of these stages has advantages and drawbacks.
Stage one sounds terrible, but there is a kind of protection implied--the fearful person may never take any risks and therefore may not excel, but they will avoid some of the negative events that befall risk-takers.
People at stage two tend to believe that everybody else is at this stage, and they don't see any problem with being selfish. In fact, often they believe that what they do also benefits the greater good (see Ayn Rand, or "What's good for General Motors is good for America.")
Stage three removes the need to make many decisions or question your actions. The path forward is defined for you by your group or your religion.
While stage four sounds great, it has just as many potential conflicts and complications as the others. For instance, imagine a scientist whose research could potentially save the lives of many people--but requires a dedication of time and effort that makes it difficult for him or her to also devote enough time to family. That's the story of many top artists and scientists.
Of course, nobody is motivated by only one of these all the time. Probably over the course of the day, we make decisions based on all four. Even the same action may be motivated by a mix. However, one may predominate.
HOW TO APPLY THIS TO YOUR CHARACTERS
You could use these as a pattern for the character arc of your protagonist. The character could go from stage three to stage four, or even from stage one to stage four, although a change that big that would require intense events to drive it.
You could also decide at which stage the other characters are. That will help you decide what they would do at any point in your story.
Finally, having different characters at different levels will tend to generate conflict, always useful when you're building a plot.
Want tips on creating outstanding characters? You'll get them from the top writers of today and times past, in Your Creative Writing Masterclass, published by Nichalas Brealey/Hachette, and available from Amazon or your other favorite bookseller.