Yet participation in the sacraments is clearly essential to salvation and theosis (John 6). Why, then, have some of the Church's greatest saints almost never participated in them?
Solomon, David, Isaiah, Jeremiah, Sampson, etc. didn't participate in the sacraments as we know them, yet are in the Lord's Kingdom. He laid out a path, they followed it. Our path has been laid out by Him, and it includes the sacraments.
St. Mary of Egypt didn't partake much, but when she did it was of "high efficacy." That doesn't make her more/less important than those who communed frequently (Sts. Basil, John Chrysostom, Athanasios, Demetrios, Peter, Paul, Nektarios, etc.). For us, the way with the sacraments is the "sure way," and the way without the sacraments is Mirkwood - you can theoretically get through it, but it's tough, with a lot of distractions, a lot of demons, fatigue, hallucinations, and a high chance of perishing.