Today, many smartphone users experience stress from receiving notifications all the time. In this work-in-progress paper, we explore the relationships between users' stress levels from receiving smartphone notifications and notification setting activeness from messenger app, and we also identify the implications to reduce stress. In order to understand the user, we selected the messenger application KakaoTalk, which is the most frequently used smartphone messenger application in Korea, and conducted an online survey of 95 smartphone user participants. We investigated how users actively set their smartphone notifications in their daily lives and how users become stressed from receiving these notifications. From this understanding, we propose design implications for notification interfaces in smartphones, in which the user can still be effectively aware of his or her notifications but can also reduce stress in his or her life.