How do we differentiate between showing off (riya') and speaking about Allah's blessings upon us?

Ostentation (riya') is seeking worldly gain through acts of worship, and it is the opposite of sincerity (ikhlas). Riya' is derived from "seeing" (ru'yah), meaning one performs an act so that people may see it. As for seeking a good reputation (sum'ah), it is derived from "hearing" (sam'), meaning one performs an act so that people may hear about it. However, speaking about the blessings of Allah is a complete form of gratitude for these blessings. Allah the Almighty commanded His Prophet, peace and blessings be upon him, to do so in His saying: "But as for the favor of your Lord, report [it]." (Quran 93:11), meaning, publicize what Allah has bestowed upon you with gratitude and praise. Therefore, speaking about and acknowledging the blessings of Allah the Almighty is an act of gratitude.