This event occurs in Chapter Four of this classic novel. Whilst Holden is talking to Stradlater, he twice says that he should go and see Jane, whom he obviously cares for very deeply, as evidenced by the amount of detail--very personal detail--he remembers from their time together. However, in the end, he decides not to. This is his reason why:
"I'm not in the mood right now," I said. I wasn't, either. You have to be in the mood for those things.
One way of reading Holden's avoidance of seeing her is his own feelings of isolation and also perhaps his fear of rejection. He clearly has strong feelings for Jane, but given his imminent expulsion from his latest school he perhaps fears rejection or a rebuffing that would hurt his fragile sense of self-esteem even further. In addition, given Holden's fear of sex and sexuality, he might not want to place himself in a situation with a girl that he obviously feels very strongly about due to his own unease about growing up and the protective way that he feels about Phoebe, his younger sister, and also Jane in this section of the novel. It is clear that Holden is bothered that it is Stradlater, one of the few sexually experienced students at his school, that is taking Jane out.