In Mark 4, Jesus describes the seed that goes into stony ground as having no depth and no root. A person who receives the gospel and does not get rooted in the word and and with prayer does not have the depth to remain.
According to Heb 2:1, we drift when we don't pay attention to the words of Jesus. The Word should be so important to us, that whether we feel like it or not - we pay attention. We listen and we do the Word - as it says in James 1.
I also like to tie this thought in with Matthew 7:21-29. Jesus was speaking to temple - attending (church-goers) - when he answered their declarations of service with "I never knew you, depart from Me, you who practice lawlessness." This is scarey! SO - read on - the difference between building your house about the rock and the sand (being known by Jesus) - is hearing and doing. so - Pay attention! He says in 1 Corth 8:3 - that He KNOWS the ones who loves us and we see in John 14:15 that if we love Him - we obey Him.
Perhaps the Word get depth and deeper roots through obedience to His Word.
He is an awesome God - and the more we love Him the more we want to obey.