A computer-implemented method, comprising: collecting a first set of data from at least one sensor of at least one user device, wherein the first set of data comprises at least one of physiological data or contextual data; collecting a second set of data comprising at least one partial or complete ecological momentary assessment response from a user of the at least one user device; establishing a set of physiological time-series data for the user based on the first set of data and the second set of data; identifying habit information related to regularly occurring habits of the user based on the first set of data; based on at least the first set of data and the habit information, detecting a potential trigger point for sending a subsequent EMA to the user, the subsequent EMA being used to ascertain a stress valence of the user at a time of the potential trigger point, wherein the detecting of the potential trigger point further comprises using the habit information to disregard physiological arousal unrelated to stress; and at the time of the potential trigger point, calculating an estimate of a stress valence value associated with the subsequent EMA for which an EMA response was at least partially not received, wherein the stress valence value estimate is calculated based on at least one of the physiological time-series data, the at least one previously collected partial or complete EMA response, the first set of data, or the habit information, wherein the calculating of the estimate of the stress valence value comprises performing backtracking to identify past trends in the physiological time-series data of the user; and wherein the performing comprises iteratively applying an increasing retrospective time window beginning from the time of the potential trigger point until a previously captured EMA response is found representing a change in physiological data, contextual data, or any combination thereof, that is similar to the significant change in the first set of data at the potential trigger point; and the calculating further comprises using a stress valence determined from the previously captured EMA response as the estimated stress valence value for the subsequent EMA. collecting a first set of data from at least one sensor of at least one user device, wherein the first set of data comprises at least one of physiological data or contextual data; collecting a second set of data comprising at least one partial or complete ecological momentary assessment response from a user of the at least one user device; establishing a set of physiological time-series data for the user based on the first set of data and the second set of data; identifying habit information related to regularly occurring habits of the user based on the first set of data; based on at least the first set of data and the habit information, detecting a potential trigger point for sending a subsequent EMA to the user, the subsequent EMA being used to ascertain a stress valence of the user at a time of the potential trigger point, wherein the detecting of the potential trigger point further comprises using the habit information to disregard physiological arousal unrelated to stress; and at the time of the potential trigger point, calculating an estimate of a stress valence value associated with the subsequent EMA for which an EMA response was at least partially not received, wherein the stress valence value estimate is calculated based on at least one of the physiological time-series data, the at least one previously collected partial or complete EMA response, the first set of data, or the habit information, wherein the calculating of the estimate of the stress valence value comprises performing backtracking to identify past trends in the physiological time-series data of the user; and wherein the performing comprises iteratively applying an increasing retrospective time window beginning from the time of the potential trigger point until a previously captured EMA response is found representing a change in physiological data, contextual data, or any combination thereof, that is similar to the significant change in the first set of data at the potential trigger point; and the calculating further comprises using a stress valence determined from the previously captured EMA response as the estimated stress valence value for the subsequent EMA.