This Hadeeth is not authentically attributable to the Prophet (sallAllaahu `alayhi wa sallam), even though, as you said, it is on the tongues of many people. It is compulsory for a Muslim to be careful about what he ascribes to the Messenger of Allaah (sallAllaahu `alayhi wa sallam) regardless of whether he ascribes to him a saying or whether he ascribes to him a deed, because to lie upon the Prophet (sallAllaahu `alayhi wa sallam) is not the same as lying upon one of us: to lie upon the Prophet (sallAllaahu `alayhi wa sallam) is to make a lie upon Allaah's Shari'ah.
From the Hadeeths that are famous among people but nonetheless have no basis are the following:
— "The love of one's home country is a part of faith."
— "The best of names are those that are praised and worshipped."
— "The stomach is a house of disease, and a good diet is the head of the cure."
What is important here is to note that we must be very careful about what we ascribe to the Prophet (sallAllaahu `alayhi wa sallam), so that we do not fall under the category of those about whom the Prophet (sallAllaahu `alayhi wa sallam) said,
من كذب علي متعمدا فليتبوأ مقعده من النار
"Whoever lies upon me on purpose, then let him take his seat in the Fire." (Al-Bukhari no. 107,110 and Muslim no. 3)
And he (sallAllaahu `alayhi wa sallam) also said,
من حدث عني بحديث يرى أنه كذب فهو أحد الكاذبين
"Whoever relates about me a saying, knowing that it is a lie, then he is one of the liars." (Muslim Al-Muqaddamah)