I know a brother who tries hard to avoid mastbation and feels ashamed each time he does it and promises Allah he wont do it again. It may be lack of will power but now the brother is extremely worried as he prays to Allah that he wont do it again but does it once a week (less than before) and says sorry again. Is this brother doomed or can the brother once and for all not do again and develop great will power not to do so as Allah is most forgiving?