We must understand that there are established acts of worship that must be performed at all times and never fluctuate, even after Ramadan like Salaah (prayer), Zakaah (obligatory charity), invocation of Allah and repentance, which Allah enjoins on His slaves when He Says what means: “…And turn to Allah in repentance, all of you, O believers, that you might succeed.” [Qur’an 24: 31] 
The Messenger of Allah, sallallaahu ‘alaihi wa sallam, used to say: “I seek the forgiveness of my Lord and repent to Him one hundred times a day.”
Now that you know this, it becomes incumbent on you to put it into practice, for you have tasted the sweetness of worship and closeness to Allah in Ramadan. Therefore, do not ruin that with your sins. Moreover, the continued observation of acts of worship or negligence in them is an indication of the inner-workings of the heart, for it is the most changeable organ in the human body. That is why the Prophet, sallallaahu ‘alaihi wa sallam, said: “The heart was given that name because of its inconstancy. The similitude of the heart is like that of a feather at the bottom of a tree which the wind blows hither and thither.” [Ahmad] The Messenger of Allah, sallallaahu ‘alaihi wa sallam, used to say in his supplication: “O turner of the hearts! Establish my heart firmly on your religion.”
It is your right to celebrate Eid for it is Allah who made joy and happiness among the rewards for certainty of faith and made sorrow and distress among the recompense for displeasure and doubt. Eid should be an occasion for wholesome recreation and amusement. It is when people exceed the limits of Allah in their celebration and harm others then it becomes unlawful. This is because in these instances, people do not give Allah His due rights, nor do they thank Him for His blessings. ‘Ali bin Abi Taalib, may Allah be pleased with him, saw some people playing around in a manner that is displeasing to Allah on the day of Eid and remarked: “If Allah has accepted these peoples’ fasting then these are not the actions of the grateful and if Allah did not accept their fasting then such is not the behaviour of the fearful.”
Ibn Al-Qayyim, may Allah have mercy upon him, said about happiness: “Surely, Allah shall bring this ware (happiness and joy) to its merchants (i.e. those who know how best to rejoice) and those who know its value, though it may, on the way, fall into the hands of those who do not appreciate its value, for many are carriers of knowledge who are not themselves knowledgeable and many are carriers of knowledge unto those who are better than them in understanding.” Allah Says what means: “The example of those who were entrusted with the Torah and then did not take it on (by neglecting their duty towards it) is like that of a donkey who carries volumes (of books)…”[Qur’an 62: 5]
The Muslim should, therefore, not exceed the limits when rejoicing for Allah does not love such people. This is because excessive joy generates arrogance and disdain for the truth. While commenting on the saying of Allah which means: “From the evil of the retreating whisperer (a devil who makes evil suggestions to man but disappears when one remembers Allah).” [Qur’an 114: 4] One of the Qur’anic commentators said: “The devil occupies the heart of man whenever he is happy or sad, but when he remembers Allah he withdraws.” So fear Allah during joyful moments for the sincere Muslim does not transgress the limits, nor does he deviate from the truth due to his happiness. Ali Ibn Abi Taalib said: “Every day in which one does not disobey his Lord is a cause for celebration.”
The Wise Law-Giver has prescribed for you the fasting of six days in the month of Shawwaal. The Messenger of Allah, sallallaahu ‘alaihi wa sallam, said: “Whoever fasts (the whole of) Ramadan and then follows it up with six days fasting in the month of Shawwaal, is like the one who fasts for the whole year (in terms of reward).” It is better to observe this fast immediately after Eid and do them in succession, but there is no harm if one separates between them or fasts them anytime during that month. These six fasts are not obligatory.
Whoever fasts them will be rewarded for that and whoever does not, will not be punished. If one is however consistent in fasting it for years and then becomes unable to do so in a particular year due to illness or travel, they will get the same reward as if they fasted them. This is because the Messenger of Allah, sallallaahu ‘alaihi wa sallam, said: “If a man is sick or travels, what he used to do while he was resident and healthy will be written down for him.”
However, it is not permissible for someone to fast these six days before they make up for the days that they missed during Ramadan. One will only get the reward for the six days fasting in Shawwaal if they have completely fasted the whole of Ramadan. Finally, let whoever wants an additional reward endeavour to fast on the 13th, 14th and 15th day of every month for the Prophet, sallallaahu ‘alaihi wa sallam, has explained that whoever fasts them is like the one who fasts perpetually. 
Fear Allah as He should be feared and be conscious of Him in private and in public. Worship Him as if you see Him, for even though you do not see Him, He sees you.
Allah Says what means: “And rely upon the Exalted in Might, the Merciful. Who sees you when you arise. And your movement among those who prostrate. Indeed, He is the Hearing, the Knowing.” [Qur’an 26: 217-220]
Article source: http://www.islamweb.net/emainpage/