Regardless of whether you believe in eternal security, the thing is: how do you KNOW that you have been saved in the first place? Even if you do believe that you can't lose it, how do you know that you have gotten it in the first place? There are plenty of Christians who said a prayer of repentance but are NOT walking in the Lord. And Jesus said: not those who call me Lord will enter heaven but those who DO the will of the Father (Mat 7)
James said: if you have faith without the evidence of deeds (which is walking in the Lord) then your faith is dead and won't save you.
So how do you know if you have saving faith?
Jesus said: you will know by their fruit.
Jesus also said that only A FEW will make it. Only a FEW walk the narrow road, although there are lots and lots of those who call themselves Christians.
So, since you don't know, you need to get close to the Lord, as close as possible. And when you really really love Him, you will not doubt your salvation anymore. And that's the ONLY way to know. If you truly truly love Him.
BUT, Mercy is Sooo NOT OVER!
Because it is through a close walk with the Lord that you receive power to stop sinning. It's the life of Jesus Christ in you that will start showing up and making you strong against your flesh and will help you not sin. BUT in order to obtain that, in order to activate that power of God within you, the one which will help you, you need to draw close to God. Spend most of your time in seeking Him.
God has made us perfect. He doesn't look at our sins anymore. He helps us in our weaknesses and gives us strength to overcome - BUT ONLY IF YOU DRAW VERY CLOSE TO HIM.
So, once you draw very close to Him, there is plenty of mercy, there is no judgement, there is comfort and LOVE LOVE LOVE.