*This is supposed to be post 3 of 3, but has turned into post 3 of 4*
In Galatians 5 verse 4 we see a reemphasis on verses 2 that if you are relying on something external as a means of any part to your salvation then you are stuck in the bondage of sin because you have fallen from grace. Now, some have abused this verse and interpreted that one could lose their salvation, which is not true.
In fact, in this particular verse it has nothing to do with losing salvation. Rather it is referring to the principle of falling away from grace. It is pointing out that you cannot combine law and grace and in doing so you have cancelled out grace. So the key is to continually depend on grace that it may abound evermore.
To clarify this point, let's say there is an individual who has clearly heard the gospel, understands the gospel, but decides for whatever reason to reject the gospel. At that moment this individual has rejected the grace of the gospel that was extended to them. According to Hebrews 6:4-6 at this moment they have fallen from grace because to come this far and be enlightened by and to taste the gospel and still reject it would be an apostasy.
Another way to simplify this would be the same scenario, but the individual believes that the only way to obtain salvation is to believe and accept the gospel, but also do x,y, and z in order to be saved. This passage shows us that the two cannot go together and therefore they have fallen from grace, in other words they were never a follower of Christ to begin with. So freedom depends on grace and no, you cannot lose your salvation that is obtained in Christ alone!