by: Husayn al-'Awaa`ishah [From the book The Book of Sincerity. Published by Al-Irshad, 1997.]
Before you take a single step - my brother and sister Muslim - it is vital for you to be acquainted with the path in which your deliverance lies. Do not exhaust yourself by performing an abundance of actions. Perhaps the one who does many actions does not gain anything except tiredness in this world and punishment in the Hereafter.
Allaah the Exalted said:
And We shall turn to whatever actions they did and make them into scattered dust.
It is He who created life and death to see which of you is best in action. 
Therefore know, prior to everything else, the necessity conditions for actions before they are accepted. It is vital that two great and important matters are fulfilled before every action. If they are not, the action will not be accepted.
The First is that the one who performed the action desired nothing but the Face of Allaah the Mighty and Majestic, by it.
The Second is that the action is in agreement with what Allaah the Exalted has legislated in His Book or His Messenger [saas] has explained in his Sunnah.
Some of the Salaf used to say: "There is no action, even if it is insignificant, except that it will have two questions put to it: 'Why did you do it?' and 'How did you do it?'
The first question is about the reason for the action and its motive. If the motive was for an objective from among the objectives of this world, such as seeking praise or status or any other worldly aim, it is an evil action and will be thrown back at its performer. If the motive for the action was to fulfil the right of Allaah - of pure enslavement to Him and seeking a means of nearness to Him, then it is a good action and will be accepted insha` Allaah.
The second question is about the following and imitation of the Messenger [saws]. Was the action from amongst the legislated actions or was it from one's innovations and invention? If it was from the guidance of the Messenger [saws] then it is a good action and if it was in opposition to the practise of the Messenger [saas] then it is an evil action and will not be accepted from its performer as is proven in the hadeeth of A'ishah [may Allaah be pleased with her] who said: "Allaah's Messenger [saws] said: "Whoever introduces into this affair of ours something that does not belong to it will have it rejected." She also reports that Allaah's Messenger [saas] said: "Whoever does an action that we have not commanded will have it rejected."
When one of the above two conditions is not fulfilled the action is neither righteous nor acceptable. The saying of the Blessed and Exalted provides evidence for this:
And whoever places his hope in the meeting with his Lord let him work righteous deeds and in the worship of his Lord associate none as a partner.
Allaah the Sublime has commanded in this verse that the action should be righteous, meaning in agreement with the Sharee'ah. Then He commanded that the person should make it sincerely for Allaah, desiring by it nothing besides Him.
Allaah the Exalted also said:
And who is better than the one who submits his face to Allaah and is a doer of good?
The meaning of submitting one's face to Allaah is: making one's intention and action for Allaah. And the meaning of doing good is: imitating and following the Messenger's [saas] Sunnah.
1.This is illustrated in the Prophet's [saas] saying: 'Perhaps a fasting person obtains nothing from his fasting but hunger and one who stands during the night in prayer, nothing but tiredness.' Reported by Ibn Majah from Abu Hurayrah and Shaykh al-Albaani declared it to be authentic in his Saheehul-Jami'I, no. 348.
2. Surah al-Furqaan (25): 23.
3. Surah al-Mulk, (67): 2.
4. Salaf: Pious Predecessors.
5. Reported by Muslim.
6. Ibid. Surah al-Kahf (18): 110.
7. Surah an-Nisaa (4): 125.