Systems and methods are disclosed for customizing a user's experience with an application such as a search engine application. The user's experience is customized based on inferring a mood and/or interests of the user at least in part from an analysis of the user's posts on one or more social media sites. The search engine application is configured to include a user-following engine which follows a user's activities on social media websites. By tracking a user's posts and other activity on social media websites, and possibly those of his or her friends, the user-following engine is able to draw inferences about a user, including for example the user's emotional state, current trending interests, future plans, likes/dislikes and aspirations. The user-following engine may then customize the user's search experience based on these drawn inferences.