Thank you for your honesty -- and I suspect many people who are reading this can identify with you. Nothing is more final than death, and once it comes to someone we know, the opportunity to express our love ... or thank them for what they meant to us ... or ask for their forgiveness ... is gone forever.
This is one reason why we need to look beyond any problems or disagreements we may be having, and do our best to overcome them. The Bible says, "Make every effort to live in peace with all men and to be holy (i.e., pure)" (Hebrews 12:14). It also tells us to learn to forgive others, even if we think they are in the wrong and we are in the right: "Bear with each other and forgive whatever grievances you may have against one another. Forgive as the Lord forgave you" (Colossians 3:13).
But we also need to learn to encourage others and help them overcome their problems. Even a quick word of encouragement may change someone's attitude and help them get on the right road in life. Don't wait until it's too late.
At the same time, never forget that someday we all will die -- and then it will be too late to seek God. Don't let this happen to you, but by faith turn to Christ and ask Him to forgive you and come into your life. The Bible says, "Now is the time of God's favor, now is the day of salvation" (2 Corinthians 6:2).