You Need to Know (Quotes from Imam Ghazali)

The danger of becoming trapped in sins

One should not undervalue even a small amount of devotion, for a large quantity which is made up of individual small acts, has an effect, so that each one of them must exercise an influence. There is not a single act of devotion but that it has an effect, even though it must therefore necessarily entail some reward, since reward is in proportion to its effect, and this is the case with sin also. How many sages there are who deem the wasting of a day and a night a paltry thing, and continue to do so, procrastinating day after day, until such time as death suddenly seizes him, or the darkness of his sin builds up in his heart that he is unable to repent (for a little ever invites one to abundance), and his heart becomes loaded with the chains of desires, from which he is unable to release himself. This is what is meant by "closing of the gate of repentance", and by Allah's statement (exalted is He!): "And We have set a barrier before them and a barrier behind them."

[From Imam Ghazali's book "On Disciplining the Soul".]