but
the pattern of salvation 要求人的 都一致,
repent
believe,

there is no SIN that is too big for God to forgive
&
there is no SIN that is too small for God forget

At that moment when John prayed as you mentioned,
he just feel sorry for what he is doing
and no plan to repent and U-turn,
comparing with King David,
he repented and never did that again,
most probably he never took a new woman again.