The teaching of sola gratia is that it is only God’s grace that accomplishes salvation. No act of man contributes to salvation in any way. This doctrine is closely associated with sola Fide, stating that faith activates saving grace. Sola gratia holds that man has absolutely no role in his salvation. That is, God saves you whether you want it or not. He also damns you whether you want it or not. This view is called monergism (“one actor,” i.e., God). These two actions together are called double predestination—both the saved and the damned are predestined to their fates. In this case, both faith and grace are gifts from God and do not involve man’s will in any way.

Most sola gratia believers are not this extreme, however; they believe that man must at least assent to salvation at some point, even if only once. Sola gratia disregards the doctrine of free will that God granted mankind from the beginning of creation. Orthodoxy believes in synergism, that God and man are co-workers: “We then, as workers together with Him, also plead with you not to receive the grace of God in vain” ( 2 Cor. 6:1, NKJV).

One of the principal problems with sola gratia is that grace is understood as something other than God Himself. In Reformation theology, grace is “unmerited favor,” an attitude in God, often contrasted with His wrath. For Orthodoxy, grace is uncreated, grace is God, His actual presence and activity. But if grace is merely “favor,” then union with God (theosis) is precluded.

The other articles on the “Sola’s” can be found at the links below:
What Is The Orthodox View On The Solus Christus Doctrine? 
Orthodox View on Soli Deo Gloria
What is the Orthodox view on the Sola ‎Fide?‎
What is the Orthodox view of Sola Scriptura?‎