Sheikh `Abd Allah al-Manî`î
Allah says: “Then anyone who has done an atom’s weight of good shall see it” [Sûrah al-Takâthur: 5]. Whoever fasts one day of these days will be rewarded for that one day . Whoever fasts the three days will be rewarded with the complete reward. Allah will never wrong anyone.
You should go ahead and do as good as much as you can and do not hesitate. Do not abandon whatever you can of good deeds. If we cannot do something fully, that does not mean we should completely neglect it.
Source: Islam Today