Luke 13:24
"You should try hard to enter [God's kingdom] by means of the narrow door, for I tell you, many people will try to enter it but will not be able to.
Hebrews 4:11
So, we should do our best to enter into that state of rest, so that no one fails [to do so] by following the same example of disobedience [i.e., as seen in the Israelites. See verses 2, 6].
Hebrews 6:11-12
And it is our desire that each one of you shows the same eagerness [to live for Christ], so as to be fully assured of your hope [in never ending life] until the end [of your days].
2 Peter 1:5
And for this very reason, you people should make every effort to develop goodness along with your faith,
2 Peter 1:10
So, brothers, be diligent to make sure of your calling and election [i.e., of your status as being selected by God], for when you do, you will never stumble [and fall away from God].