This is a vital doctrine that must be clearly understood.  Even among
Evangelicals there is much debate as to the meaning and defining of such
term.  Once a believer understands the concept of salvation he will begin
to appreciate all that God has done for him.  This then should "motivate"
believers to accelerate in their walk with God.
Eternal security is discussed as well as assurance.  Be sure to be
familiar with these terms because they are subject to discussion among
Christians.

For an extensive treatment of this doctrine we recommend Chafer's eight
volume Systematic Theology.