Why does Pip go to the marshes at the beginning of Great Expectations?

When the offer comes, Pip is disillusioned with his future as a blacksmith. Because of the time he spends with Miss Havisham and Estella, he is ashamed of his common origins and his "lowly" position. Estella scorns him, and he has a major crush on her, so he doesn't want her to have any reason to scorn him. He already thinks often about becoming a gentleman so that he is worthy of Estella. When the offer comes, it is exactly what he thinks he needs to complete his fantasy of a perfect life.