This is the 6301st most frequent Russian word.
успешными
"Successful."
Here, "успешными" is in the instrumental plural form because it describes the subject's state achieved through transformation ("стали").
Мы стали успешными в нашей новой работе.
We have become successful in our new job.
In this sentence, "успешными" is used as an adjective in the instrumental plural form for motivational context.
Важно быть успешными в своей карьере.
It is important to be successful in one's career.
"успешными" here describes the state of the children in the instrumental plural form, indicating the result of their growth.