It is good to say "I will not sin today", but if you really mean "I will revisit this again tomorrow", that is not as good as saying "I never want to do this sin ever again. Delaying potential defeat is not as good as getting victory over a sin.
Ni vema kusema "Sitafanya dhambi leo", lakini kama unamaanisha kweli "Nitaliangalia jambo hili tena kesho", kusema hivyo si vema sana kama kusema "Sipendi kufanya dhambi tena." Kuahirisha anguko lenye uwezo wa kutokea si jambo jema kama kupata ushindi dhidi ya dhambi.