Do discharges resulting from pleasant conversations, the occurrence of exciting thoughts and scenes, or wet dreams necessitate ghusl, and do they affect the validity of fasting and acts of worship?

Normal secretions unrelated to desire are pure, invalidate ablution (wudu'), and do not necessitate ritual cleansing (istinja (definition)'). As for secretions related to desire, they are pre-seminal fluid (madhy), which is impure and invalidates ablution. The emission of pre-seminal fluid merely from talking or looking does not invalidate the fast; the correct view is that the emission of pre-seminal fluid does not invalidate the fast at all. Ritual bathing (ghusl (definition)) is not obligatory unless the woman is certain of the emission of semen after waking up from sleep.