Here's what I've learned: in general, emotional motivation tends to be stronger than logical motivation. For instance, say your character is trying to save the world. "Trying to save the world" is motivation, but it's not particularly interesting. (I should know. In one of my earlier books, the main character had this exact same motivation....save the world.) That is, unless there's some emotional component attached. Take, for instance, Harry Potter. Possibly not the best example in the world, but Harry's determination to take down Voldemort certainly has an emotional component: his parents. Voldemort killed his parents and deprived him of a childhood. This motivation is far more empathetic and interesting than a boy who simply wants to do the right thing.
At every moment in the book, your character should want something. Oftentimes a book's main plot might not start until a little ways into the story (i.e., Harry isn't determined to take down Voldemort until about halfway through Sorcerer's Stone). However, even before the character's most pressing goals actually surface, they should desire something at all times. In the beginning of Sorcerer's Stone, Harry wants desperately to escape the Dursleys. This want gives us the opportunity to connect with Harry through similar emotions.
Anyways. Those are my ramblings of the day. Hope everyone's had a great week!