Does falling away from the faith mean you were never really saved in the first place? (1 John 2:19)

Many Protestants teach that you cannot lose your salvation, so when a person "falls away" from the faith, some of these Protestants conclude that this person was never really saved in the first place. Their favorite prooftext for this claim is 1 John 2:19. Their interpretation is quite convenient, but is actually quite unreasonable, and it's is hurtful towards Christians who struggle with sin (thinking they might never have been saved). 

To begin, consider the context of 1 John 2:19,

18 Children, it is the last hour, and as you have heard that antichrist is coming, so now many antichrists have come. 19 They went out from us, but they were not of us; for if they had been of us, they would have continued with us. But they went out, that it might become plain that they all are not of us.

These Protestants read 2:19 as saying these people who "went out" of the community by apostasy demonstrate that they never really were saved, since true Christians remain in the community. This interpretation is somewhat understandable, but it is very weak when you consider the context, the Greek words themselves, similar verses, and theological coherence. 

This simple picture helps explain "Divine Simplicity" and God's many "attributes".

This post is more of a theological reflection rather than an apologetics argument. Oftentimes I've heard people talk about how God is "both infinitely Merciful and infinitely Just," or some similar comparison, as if God somehow was able to hold together many conflicting "attributes" at the same time. I think the answer to these kinds of questions is to recognize that what we think of as God's "attributes" are only half the picture. Consider the following diagram:

This is a picture of White Light (sunlight), which is invisible to the human eye, but when this White Light hits a Glass Prism, the White Light reflects off it and result is the spectrum of the colors of the rainbow. (This is real science you can do at home.) 

The analogy to draw from this example is that God is similar to the White Light in that He is normally invisible to us, while the Prism is similar to Creation, and when God interacts with Creation we see Gods many beautiful attributes throughout nature and in divine revelation. The point being that the colors of the rainbow represent God's attributes, such as Justice, Mercy, etc, and these are truly distinct from Creation's point of view, but in reality these terms are only human terms to describe an ultimate reality (White Light) that is far beyond our mind's ability to grasp. This is one reason why Christian theologians throughout history have described God as "simple," not to suggest God is easy to understand, but rather to say that God isn't composed of many 'parts'. We cannot really fathom or understand God directly, but we can still understand Him 'indirectly' in a real and true manner.