Introduction: Positive psychological's constructs have shown a direct effect on adherence to pharmacological treatment, diet, physical activity and general commitment to health, in the same way that negative ones, such as depression, anxiety and stress, are associated with worse cardiovascular outcomes and are prevalent in patients with infarction. Objective: To verify whether a gratitude intervention can improve self-care and improve negative psychological states in patients with recent myocardial infarction. Methods: Randomized, parallel clinical trial. The inclusion criteria will be patients with ST-segment elevation myocardial infarction (STEMI) with less than 12 hours of evolution and undergoing primary percutaneous coronary intervention (pPCI). Participants will respond to the socio-demographic and risk factors questionnaire and self-care (ASA-A), anxiety, depression and stress (DASS-21) and gratitude (QG-6) scales. They will be drawn into the gratitude intervention group or neutral events group according to the randomization list. Patients in the intervention group will be tasked with writing down 3 to 5 situations a day for which they are grateful, for 14 days. Patients in the control group will be asked to write down 3 to 5 situations a day that have impacted them, whether good or bad. Both groups will be reassessed after the intervention and after 6 months. Expected results: It is expected that the intervention group will improve self-care and the feeling of gratitude, modify behaviors and decrease negative affects, while the group without intervention will remain unchanged from the beginning of the study to 6 months.

Study design: Randomized, parallel clinical trial. The study will use a prospective experimental design with Condition and Time as independent variables. The condition has two levels that correspond to the experimental conditions: (a) Gratitude List (aspects of daily experience that one feels grateful for), (b) Any Event List (events of one's own choosing that impressed the participant during the day, whether positive or negative). Time is a repeated measures variable with three levels corresponding to the measurement times: (a) Pre-test (before the intervention), (b) Post-test (at 2 weeks after of the intervention - visit 1) and (c) ) Follow-up (from baseline to 6 months - visit 2).

This follow-up period is based on the previous studies. Patients will be invited to participate in the study during hospitalization for AMI. If they agree to participate, they must sign the Free and Informed Consent Form. They will answer the socio-demographic questionnaire and risk factors and self-care scales (ASA-A), anxiety, depression and stress (DASS-21) and gratitude (QG-6).

Envelopes will be opened after the initial interview. Participants will receive instructions for the intervention. Participants will be asked to allocate 10-20 minutes at the end of the day, before bed, for 14 days, to write the lists, according to their allocation group. Studies involving gratitude interventions generally last for two weeks as already explained.

In each group, participants will make a list of up to five items, evaluating the activities of that day. The instructions for the groups were adapted and translated.

For the intervention group (Gratitude List), the instructions will be:

"During the day, many things happen in our lives, big and small, for which we can be grateful. Think about your day and write down up to five things in your life that you are grateful for."

For the control group (List of any event), the instructions were:

"During the day, there are many events in our lives, big and small, that end up affecting us. Think about your day and write down up to five things in your life that affected you." Patients will receive a small notebook for daily notes, starting on the day of discharge. Upon discharge, text messages will be sent to their cell phones with reminders not to forget to start and continue making lists. At the end of 2 weeks of the intervention, patients will be invited to return for a reassessment interview (visit 1), and again at the end of 6 months (visit 2). A 6-month follow-up will be necessary so that we can assess changes in behavior.

To assess the improvement in self-care, the ASA-A scale will be used. To assess emotional factors, the DASS scale (which assesses anxiety, depression and stress) will be used. To assess gratitude in the face of life events, the QG-6 scale and for physical health, a dedicated questionnaire will be used. All scales will be used before and after.

Inclusion Criteria:

• ST-segment elevation myocardial infarction (STEMI) patients
• Undergoing primary percutaneous coronary intervention (pPCI).

Exclusion Criteria:

• Patients in need of ventilatory support;
• Over 75 years of age;
• Delirium or dementia reported by the attending physician.
• Not able to answer the questionnaires.
• Very high depression scores requiring referral to psychological care services

Neither the researcher nor the participants will be blind to the group to which they were allocated. Because the first will give the necessary guidance and the second will have knowledge of the existing groups through the TCLE and at the time they receive the instructions. Blinding will only occur for the research participant (scientific initiation scholarship holder or volunteer) who must carry out the return interviews and the application of the questionnaires soon after the end of the intervention and in the 6-month follow-up.

Primary outcome: Self-care and negative psychological states Secondary outcomes: Change in behavior (physical activity, diet...) and gratitude.