allah, the exalted, says:

"verily, allah will not change the (good) condition of a people as long as they do not change their state (of goodness) themselves (by committing sins and by being ungrateful and disobedient to allah).'' (13:11)

"and be not like her who undoes the thread which she has spun, after it has become strong.'' (16:92)

"... lest they become as those who received the scripture [the taurat (torah) and the injeel (gospel)] before (i.e., jews and christians), and the term was prolonged for them and so their hearts were hardened?'' (57:16)

"but that they did not observe it with the right observance.'' (57:27)

692. `abdullah bin `amr bin al-`as (may allah be pleased with him) reported: messenger of allah (pbuh) said to me, "o `abdullah! do not be like so-and-so; he used to get up at night for optional prayer but abandoned it later.''
[al-bukhari and muslim].

commentary:  this hadith also stresses the same point, that is, man should be steadfast in his good doings. there should be no cessation in this respect, otherwise, he will unconsciously begin to incline to evil and, therefore, to the erosion of moral foundations of his character. steadfastness in the observance of good ensures man's security against pitfalls and has divine approval, too.