Fasting is patience in obeying Allaah, patience in keeping away from the things forbidden by Allaah, and patience in bearing the decree of Allaah, hunger, thirst, physical and mental weakness.
Make use of this month, Know its value and Estimate its worth. Respect it and spend its time in acts of obedience and worship, for this opportunity will not last. Nothing remains except the living and eternal (Allaah). So you will not remain and neither this month nor its days will remain.
With regards to fasting that is accompanied by sins, the fast is not invalidated by that, rather it is valid and the fasting person has fulfilled his obligation and does not have to make up the fast.
Shaykh Saalih ibn al-Fawzaan (hafidhahullah) and Shaykh Muhammad ibn Saalih al-Uthaymeen (rahimahullaah) explains as to what is special about fasting that Allaah has singled it out from other acts of worship by his statement “Fasting is for Me and I shall reward for it”?
Weak Hadeeth – Beginning of Ramadan is Mercy, its Middle is Forgiveness and its End is freedom from the Fire
The alleged hadeeth “The first part of the month of Ramadaan is mercy, the middle of it is forgiveness and the end of it is freedom from the Fire” is a well known, albeit a very weak narration.
Shaykh Saalih al-Fawzan (hafidhahullaah) clearly explains as to where one should devote his time towards in Ramadan and as to why Ramadan is not the month for sleeping during the day, for spending all the time in the marketplaces and abandoning the masaajid, for begging etc.