Is it true that thinking about feelings of joy and happiness that were associated with watching TV series or listening to prohibited songs, and remembering their melodies, could lead to a return to sin, and is this kind of thinking forbidden?

Allah does not hold a servant accountable for thoughts unless they are acted upon or spoken. However, prolonged dwelling on the past and recalling the pleasure of past sins may lead to their repetition. Salvation lies in guarding one's thoughts and occupying oneself with what benefits in both religious and worldly matters.