Using large proprietary money management app data from a major commercial bank in Canada, I study how the app users manage their personal finance upon seeing an overspending message on the mobile app. First, I find that the message recipients reduced spending on the following day by C$8.15, which corresponds to 5.4% of their daily average spending, compared to the non-recipients. Second, these fintech nudges had temporary effect on flow spending and resulted in permanent reduction in cumulative spending. Third, the effects are especially pronounced for the users who are older, have higher liquid wealth, are more finance-savvy, are new to the app experience, or reside in a city with a higher fraction of educated population. Fourth, I find suggestive evidence that these effects could spill over from one app user to another in the same household. On the other hand, the message recipients were less likely to monitor their accounts via log-ins afterward, which is selective inattention known as the ostrich effect.