When Pip goes to see Miss Havisham and Estella presumably for one last time, he tells Estella once again about his love for her. She shakes her head at his confession and tells him that he will get her out of his head in a weeks time. To this, pip replies, “Out of my thoughts! You are part of my existence, part of myself” (Chapter 44, Paragraph 70). Pip has become so consumed with his love for Estella that he feels something is missing when she is not around. This reminds me of Wuthering Heights when Catherine tells Nelly that she is Heathcliff. The two are so intertwined that they are one in the same.
Further in Pip’s confession he remarks that he sees Estella, “on the river, on the sails of the ships, on the marshes, in the clouds, in the light, in the darkness, in the wind, in the woods, in the sea, in the streets” (Chapter 44, Paragraph 70). He is so in love with Estella that he sees all of the good things about her in the world around him. This also occurs in Wuthering Heights when Heathcliff is lamenting over Catherine. He is haunted by the natural world because he sees Catherine in the clouds and the trees as well. Both men are surrounded by the images of their loved ones which I think goes to show the depth (or obsession) of the love the characters have for one another.