"The Bible doesn't say that!"...Well actually it does...

Modern doctrine adherents will say..."it doesn't really say that"...

They will say something like..."what it really means is, once you are saved you are always saved"...

Uh, no it doesn't.  It says exactly this:

Take heed, brethren, lest there be in any of you an evil heart of unbelief,

in departing from the living God.

[13] But exhort one another daily, while it is called To day;

lest any of you be hardened through the deceitfulness of sin.

 [14] For we are made partakers of Christ,

if we hold the beginning of our confidence stedfast unto the end;

[15] While it is said, To day if ye will hear his voice,

harden not your hearts, as in the provocation.

Hebrews 3:12-15

The literal context infers that one has to be with the living God in order to be able to depart...

It is saying that this is a real potential if we hold the beginning of our confidence stedfast unto the end.

This literally contradicts anyone who insists that salvation is unconditional.

"If" is a very conditional word.

This isn't  the only place were this is seen in the Bible. It's not hard to find them. Try looking for them on  your own and then go ask your pastor why he is teaching nonbiblical doctrines. Ask him, 'who else taught this before Calvin?'