Is it necessary to repeat ablution if one experiences secretions afterwards due to thinking or watching television?

The discharge resulting from looking or contemplating lust is usually madhy (pre-seminal fluid), which is a thin, sticky, whitish fluid that is discharged when desire subsides. Madhy is impure and nullifies wudu (ablution). If you are certain that it was discharged after performing wudu, then the wudu is invalid and must be redone. However, if you are not certain of its discharge, then the wudu is valid because the basic principle is that it is not nullified except with certainty. It is obligatory to guard one's gaze from looking at what is forbidden, in compliance with the words of Allah Almighty: "And tell the believing women to lower their gaze."