Hazrat Moulana Ashraf Ali Thanwi (rahmatullahi ‘alaih) once mentioned:
Engaging in zikr (the remembrance of Allah Ta‘ala) is a means of one acquiring great barakah (blessings of Allah Ta‘ala in his life). However, the complete effect of this zikr will only be seen when one refrains from all sins and evils.
For example, if one does not perform his fardh salaah, but performs nafl salaah, then though he will receive some reward for his nafl salaah, on account of him neglecting his fardh salaah, he will be sinful and this will cause weakness in all his other ‘ibaadaat. Hence, he will not find the desired benefit through his nafl salaah. In other words, on account of one neglecting his faraa-idh, he will not find the desired effect and reward in all his other aa’maal (righteous actions and ‘ibaadaat).
(Malfoozaat Hakeemul Ummat 2/164)
Source: Ihyaauddeen.co.za