Reference: al-Fawaa.id – p157
al-Imaam Ibnul-Qayyim (rahima-hullaah) said:
The principles upon which true happiness of the worshiper is built are:
Tawheed – the opposite of which is shirk (to associate a partner in worship with Allaah);
Sunnah – the opposite of which is bid’ah (to introduce into Islaam an act of worship which was not legislated by Allaah and the Prophet (sal-Allaahu ‘alayhi wa sallam));
Obedience – the opposite of which is ma’siyah (to sin and transgress against the Law of Allaah).