It is as if at-Tirmidhiyy is saying that after hearing what is in this book, i.e. ash-Shamā’il al-Muĥammadiyyah (الشمائل المحمدية) (the Depiction  of Prophet Muĥammad)  you now know the different merits and situations of the Messenger of Allāh, and so you should hold fast to what you have heard – follow the Prophet’s footsteps and take him as an example. One’s righteousness is by following the Messenger of Allāh. One would not be among the people of Paradise except by following the Messenger of Allāh ﷺ. Regardless of what people like or dislike, follow what came with the Messenger of Allāh.