When Ananias sold his property and gave a portion of it to the Church, he sinned--not in holding back, but in appearing to give all when he didn't. Barnabas had just sold all of his property and given it to the Church. However, Barnabas had apostolic grace and calling. Barnabas could sell all his property and give it to the Church (without fear and without pride) because he had the grace and calling of an apostle. Ananias did not.
Perhaps Ananias thought that he could do what Barnabas did. Perhaps Ananias thought, "If Barnabas can do it, I can do it." Perhaps he saw the godliness and grace of Barnabas and thought, "if only I do what Barnabas does, then I too will find the grace that Barnabas has found." Perhaps Ananias got the cart before the horse, thinking he could do what a holy man does to become holy too. But then there is the glory part. Barnabas was publicly honoured--or at least widely known--for his act of dispossession. Barnabas could handle it because of who he was, the grace in his heart, and the calling of his life. Ananias couldn't. In fact, I think it was the very expectation of honour (even before the act), that was at work in Ananias impelling him to attempt an ascetic labour too great for him.
Orthodox Christians, in my experience, are often tempted the way Ananias was. Those who are devout, who attend services, read the lives of the saints, and who strive for holiness are sometimes tempted to think that they too can fast or pray or accomplish the great ascetical labours of the saints whom they admire--just because they will to do it. This is a great delusion.
The starting point is poverty of spirit, not will to do.