1. A text message processing system for use in a mobile environment, the system comprising: a mobile messaging application for processing user text messages during a user messaging session; a user state model characterizing a cognitive load of the user based upon situational parameters including vehicle sensor information for a vehicle driven by a user, wherein the situational parameters are dependent upon user action, wherein the situational parameters include passenger compartment environment and vehicle speed, wherein the system determines, using a processor, a plurality of distraction levels from the situational parameters, wherein each of the plurality of distraction levels corresponds to the cognitive load of the user, wherein a first one of the distraction levels is based upon a first one of the situational parameters corresponding to the passenger compartment environment and a second one of the distraction levels is based upon the vehicle speed; and a functionality control module for adjusting functional performance of the mobile messaging application based on the distraction levels, such that a first one of the plurality of distraction levels corresponds to no message playback at all and a second one of the plurality of distraction levels corresponds to not playing back a message having a low priority.