After his first reign as king for a year in 1701, he abdicated the throne of Imereti, being unable to tolerate the influence of his father-in-law Giorgi Abashidze.
On Giorgi's death at the battle of Rokiti against King Alexander IV of Imereti in 1684, Mamia joined his brothers in exile in Akhaltsikhe under the protection of its Ottoman governor Yusuf-Pasha.
In the subsequent infighting between Mamia's elder brother Kaikhosro and his paternal uncle Malakia, the former lost his life, while the latter was deprived of his sight.
Eventually, in 1689, at the request of Guria's nobility, Mamia was summoned from Akhaltsikhe and installed as prince-regnant with the pasha's support, while the blinded Malakia was made Bishop of Shemokmedi by the new Gurieli ruler.
Abashidze, supported by the Mingrelian regent Giorgi Lipartiani, marshaled his troops on the borders of Guria and requested that Gurieli kill Simon, promising to make Mamia king of Imereti.
Abashidze controlled royal domains, revenues, and nobility, while Mamia had to sell his Gurian subjects in slavery to meet his own expenses.
Eager to tighten a loosening grip over their Caucasian subjects, the Ottomans mounted a large-scale invasion, with the intention to eliminate the sovereignty of Guria and limit that of Imereti.
After the death of Mamia, she married his husband's rival King Giorgi VII of Imereti, but died shortly after the marriage and was buried at Gelati.