Is it possible for the main character to have a small goal in the beginning of the book but to shelf that goal until the resolution, for a goal that is more important.
And can the character make this decision in the second act? Is that too late to replace the first goal? Answer:
Characters can have personal goals as well as be involved in the quest for the story goal.
Of course, it is a good idea to have a connection between the main character's personal goal and the story goal.
For example, you may recall the film Back to the Future
. The story goal is to reform the present (awful) situation of Marty and his family, which is done when Marty goes back in time and changes the way his parents first get together.
At the same time, Marty's inner journey concerns his learning to pursue his dream of becoming a rock musician. In the beginning he is too insecure to submit his demo tape. But by the end, he is performing on stage and inspiring Chuck Berry. And it is his courage to play his guitar that saves the day and gets his parents together.
In addition, there is a smaller goal which Marty has at the beginning of the film. He wants a car so he can take his girlfriend to the lake and cement their relationship. In the end, because Marty's intervention in the past gave his father the courage to stand up to the bully, Biff, and pursue his dreams, Marty's father is able to buy Marty the new truck he has been dreaming of, giving Marty the means to achieve this little goal.
So you see how all these goals are interconnected. Had Marty not gone on the journey to the past, he would never have gained the confidence to share his music, nor would his father have had the means to give Marty the truck.
When the audience or reader of a story sees the interconnectedness of the various goals and events, it helps give the story a sense of meaning.
As for when the character can make the decision to pursue a goal other than his personal goal... obviously the main plot is going to intrude on the character's life and force him to get involved. This generally happens at the second driver (end of act one) but becomes more cemented by the third driver (end of act two in a four-act structure).
For instance, when Marty gets sent into the past, he has to deal with that problem and the matter of the truck is forgotten until he returns to the present.
Best of luck.