Turn from your sins and stop sinning, or at least try real hard
Well, first of all, even if we tried, you, me, nor anyone else could stop sinning! Even if you could stop or make a good effort, it does not pay for what you have already done. And stopping or trying to stop will not give you the righteousness God requires to get into heaven.
"And there shall no wise enter into it (Heaven) anything that defiles, neither whatever works abomination or TELLS A LIE."
Revelation 21:27
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"But we are all as an unclean thing, and all our righteousnesses are as a filthy rags [before God]..."
Isaiah 64:6