Hebrews 12:14 KJV
Follow peace with all men, and holiness, without which no man shall see the Lord:
Let's get some things right from the very start: no matter how sweet, interesting, bitter, terrible or beautiful your life may be now, it is a phase that will end soon. It does not matter how long you have been in that phase, it will definitely come to an end. There is a purpose to all that we are going through and it is God's will that we end well. All that we do, say or think now are the building blocks towards that which God has prepared for us.
One important conclusion: nothing is as important as where you end up. It is always good to start well but it is better to end well. The world tells us that possessions, power and position are good, and so, because we have allowed the world to dictate our own lives, we spend so much time and energy pursuing these ephemeral things. Atimes, people kill others to get these things, forgetting that at the end, these things have no eternal value.
God has shown us what is important and necessary. He has told us in clear terms what we need to do and how we need to live if we are to end well. Note that there is an AND that joins the following peace together with holiness. Can a man claim to be holy, yet he's keeping malice with another? Can a man live in peace with another, while he's busy at adultery or fornication? Holiness and peace are attributes of God himself and all who claim to know him must live by his standards. You cannot claim to know God and fail to live according to his dictates. You can't give your life to Him and still choose who to love, who to talk to, who to relate with. You can't be in God and live by standards that are outside of him.
The warning that ends the extract is clear enough- without both, NO MAN shall SEE the Lord. I'm not sure you fully comprehend what this means so let me break it down again: Heaven is for those who live according to God's standards, not the world's. If you want to see and live with him in eternity, then live by these standards. Nothing else will matter when this life ends; you can't take anything with you. Live right now, live according to standard. Heaven is real, it has conditions for entry. His time of favour is here.