Assalam alaikum,
In Sahih Muslim, the Messenger of Allah, may Allah bless him and grant him peace, was reported to have said:--

''HE IS SUCCESSFUL WHO HAS ACCEPTED ISLAM, WHO HAS BEEN PROVIDED WITH
SUFFICIENT FOR HIS WANTS AND BEEN MADE CONTENTED BY ALLAH WITH WHAT
HE HAS GIVEN HIM''. (Muslim)

These days when people say so and so is very successful, what they mean is he/she is making a lot of money. By this Hadith, we understand that the one who qualifies to be called successful is NOT the one having car x or house in y and a job z but the one who:--
(a) Believes in and faithfully practices Islam (b) Whose needs are fulfilled, and (c) Who possess a thankful heart.