One of the biggest heresies on here is OSAS. Its proponents don't use scripture to support their position. It's usually something along the lines of: "How much sin is too much?" or "How many times do I sin before I lose my salvation?" 
Those aren't the correct questions. The answers people provide are just as bad. The proper way to think about whether or not OSAS is true is this:
Romans 6:1-2
What shall we say then? Are we to continue in sin that grace may abound? 2 By no means! How can we who died to sin still live in it?
Romans 6:12-14
12 Let not sin therefore reign in your mortal body, to make you obey its passions. 13 Do not present your members to sin as instruments for unrighteousness, but present yourselves to God as those who have been brought from death to life, and your members to God as instruments for righteousness. 14 For sin will have no dominion over you, since you are not under law but under grace.