Positive thoughts come when the positivity surrounds a person. Yes, first you have to surround yourself with the positive vibes. You will think about positive thoughts your ambiance surrounded by positive vibes, positive views, narrow minds, career-oriented persons, positive humans. You can get positivity in yourself.
It is difficult to think about something positive because nowadays, worst to worst cases are happening with every other human. May Allah protect us from such worst happenings. As there as a phase- “Be Positive,” which means a person should always to stay positive in bad times.