Estella, whose name means "star," is just that for Pip: a distant idealized being. From the first day that he met this beautiful girl, Estella has stolen his heart; Pip has idealized her, and no amount of behavior to the contrary will ever convince Pip that Estella is not attainable.
I never had one hour of happiness in her society, and yet my mind all round the four-and-twenty hours was harping on the happiness of having her with me unto death.
Clearly, Pip deludes himself. He knows that Estella uses him to elicit jealousy from her other admirers according to Miss Havisham's desires, but he feels his benefactress has reserved Estella for him when Estella is finished wreaking revenge for Miss Havisham.
I saw in this, a reason for her being beforehand assigned to me
Pip accompanies Estella to picnics, various fetes and orchestral gatherings, but to no avail. She tries to warn him about her, but he does not listen because he feels she will be in his arms in only a few years. Estella even asks him why he does not follow her warnings. But Pip perceives "through a glass darkly" and only feels that Estella is destined for him alone. He is bewildered and blind to any other motives otherwise.