A powerful tool in your writing arsenal is temptation.
Obviously, this doesn’t play out in every book you write. When I think of different storylines in movies and TV, not every character is tempted to make a decision that has the potential to hurt others or themselves.
If you offer the main character a temptation, it has to be something that has the greatest impact for his specific personality. It has to be something that tests their character. For example, in one of my books, I had an ex-prostitute who was struggling to make her life better. Her big goal was to be someone who was deserving of respect. So in choosing her temptation, I had to pick something that would make her seriously consider going back into prostitution. And this something happened to be hunger. She worked hard to earn money, but her employer was stingy and didn’t pay her the full wages. After a couple of weeks of battling hunger, she had to face the temptation of reverting back to her old life so she could buy food. (To this day, that is still my favorite book because of the power of temptation in it.)
The more you can make your character suffer up to the point of temptation, the more impact that temptation will have. Think of a time in your life when you were pushed to the very limits where you didn’t think you could keep going. Everything that could go wrong was going wrong. All you dealt with was stress upon stress upon, and just what you thought you couldn’t take it anymore, there was even more stress thrown your way. Your nerves were on edge. You were at the point where you felt as if you’d reached a path in the road, and either choice you chose was going to be the wrong one. This is the point the character needs to be at in order for the temptation to have its greatest impact.
Also, keep in mind your character’s motive could be good, except he’s tempted to do something bad in order to obtain get to the goal. A great example of this is the movie John Q. with Denzel Washington. This movie is about a man who holds hostages in a hospital (a bad thing) for the sake of saving his son’s life (a good thing). The effectiveness in this type of temptation is that the reader will sympathize with the character’s plight. Even though the character might do something horrible, he is doing it for a noble cause. The reader will be pulled in polarizing directions. While the reader wants the good thing to happen because of the suffering the character is going through, the reader also knows the potential for harm if the character goes down this path.