2 Peter 1:4  “…exceeding great and precious promises…by these ye might be partakers of the divine nature…”
Promise of salvation.  Promise that our sins are forgiven and are no longer held against us.  Promise that when our bodies fail on this earth, we will find ourselves with Christ.  Promise that our bodies will be resurrected into a new incorruptible form.  Promise that if we are alive when Christ returns, we will be instantly transformed into His incorruptible image to live with Him forever.  Exceedingly great and precious indeed.

5-7  “…add to your faith virtue…knowledge…temperance…patience…godliness…brotherly kindness…charity.”
Christian growth.  Once we have accepted Christ by faith, we continue to grow toward being like Him.  I wasn’t sure of the definition of virtue so checked with commentary.  It suggested moral excellency.  After that, you can see the progression.  We trust Christ, we desire to be like Him so we live by His standards.  To do this we increase our knowledge of Him.  This allows us to put to death the desires of the flesh by exercising self control.  We then endure hardship with patience, allowing Him to use it to mold us.  Our walk with Him becomes closer, and we are able to treat our brothers with compassion.  Eventually, we learn to love our neighbors as ourselves, getting us to being like Him.  Each step establishes the previous and makes way for the next.

9  “…he that lacketh these things is blind…hath forgotten that he was purged from his old sins”
We weren’t redeemed just to sit and wait until we can enter Heaven someday.  God intends for us to grow, to be transformed into the image of His Son.  There is far more to salvation than just soul fire insurance.

10  “…give diligence to make your calling and election sure…”

12  “…I will not be negligent to put you always in remembrance of these things, though ye know them, and be established in the present truth”
Repetition is learning.  The things of God are so deep, so rich, we must be diligent to continue in them until we join Him.

14  “…shortly I must put off this my tabernacle, even as our Lord Jesus Christ hath shewed me”
Reference to what Christ said to Peter in John 21:18-19.  Peter obviously recognized the signs of what Jesus predicted.

15  “…I will endeavour that ye may be able after my decease to have these things always in remembrance”
Expressed care for those with whom he was communicating.  Also, leaving a legacy behind.  After we are gone and those remaining see what we left behind, will what they see point them to Jesus?

16-17  “…we have not followed cunningly devised fables…but were eyewitnesses of His majesty…He received from God the Father honor and glory…’This is My beloved Son, in whom I am well pleased.’”
What Peter has been telling his readers is the truth.  The story of Christ is no fable or new religion.  Peter himself was a witness to the affirmation of God upon Christ while He was here.

18  “…this voice which came from heaven we heard, when we were with him in the holy mount”
The mount of transfiguration where Peter, James, and John saw Christ transfigured and Him speaking with Moses and Elijah.

20-21  “…no prophecy of the scripture is of any private interpretation.  For the prophecy came not in old time by the will of man: but holy men of God spake as they were moved by the Holy Ghost”
Scripture itself comes from God, not from man, even though God had mankind involved in writing it down.  I have spoken with folks who claimed to be teachers of the Word who said we could not be sure of what is written because man was involved.  God is more than capable of making sure His word remains true.
Also, there is no division in God.  He does not tell one person one thing and another person something entirely different when it comes to His nature.  He inspired holy men to write down His word, and all can read and understand.  He may direct some things toward one group and others to another group, but the core meaning and intention is there for all to see.

I hope you enjoy reading and studying His word.  May it accomplish what He desires.  Please feel free to comment or post questions.  Thanks for reading!