Strive to enter through the narrow door. For many, I tell you, will seek to enter and will not be able.
Pay attention to what you hear: with the measure you use, it will be measured to you, and still more will be added to you. For to the one who has, more will be given, and from the one who has not, even what he has will be taken away.
Jesus
Being a faithful Christian is about being a growing Christian. There is no coasting into heaven. We strive to enter. This isn't about stressing about the future. But it is about working at following Jesus. Doing that is hard. It takes effort. Unrepentant failure here will be fatal. Jesus warned us that there will be many who will expect to enter on the last day but won't. Those who do work at this will be blessed with 'more'. (Grace!) The result is that they will be able to do even better when it comes to working at following Jesus.
However, as Jesus warns, when it comes to those who fail to work at it, 'even what he has will be taken away'. Instead of growth and development as a disciple, the ability to follow Jesus will dribble away. This is not just some natural consequence. It will be 'taken away' by the Spirit. This is the matching curse to that blessing of grace.
The disciple's situation is not static: 'Once you're in, you're in.' Following Jesus is a dynamic relationship. That is, there is movement in the relationship. Things don't stand still. Every disciple of Jesus is either growing or fading. I fear that this is an aspect of being a disciple that is being missed by too many.