Jesus wasn't saying that we'd lose our salvation but that we could lose the chance to leave before judgment falls upon the earth in the tribulation period. He was concerned about the timing with which it would be our turn to escape the horrors of the tribulation. There is nothing of self-righteousness here. In honesty we are continually appalled to recall how truly unworthy of His grace we have been and how extremely difficult it continues to be to keep accounts current with Jesus and with our fellow man. We are not trying to earn salvation.
Salvation is by grace alone.
We are rewarded for the life we have lived and the good that we have done for the Kingdom of God and for other people. That is what Jesus was talking about with His warnings. Soldiers who are guilty of dereliction of duty are court marshaled. We all have been derelict at one time or another. There also are times when it is impossible in this life to rectify our errors.