I saw a video recently from a woman in her 80's who makes YouTube content for seniors. I really felt like it was a great example of the kind of wisdom we should be cherishing from our elders. They have lived through a lot of life, and have a lot of experience to share. Here is her advice (taken from "Life over Sixty with Sandra" - link at bottom of post) of mistakes to avoid in life:

1) Don't wish your life away If you have desires, pursue them! Act with the fierce urgency of now rather than wishing and daydreaming your life away.

2) Don't forget to say "I love you" It's easy to assume that others know that you care about them, but that's not always so. Be free and generous with expressing your love.

3) Don't dwell in bitterness In life, there will be people who will betray you or break your trust. If you let your bitterness over it persist, if you carry that grudge, you're letting them live rent-free in your mind. That hurts nobody but you

4) Don't have regrets The past is in the past, and cannot be changed. Also, you wouldn't be the wonderful person you are now, if you had made different choices! Regrets are bitterness about past choices, and as the previous point says, bitterness does you no good.

5) Listen to your intuition It's usually correct. Trust your guts, but filter it through your brain. Common sense and intuition will carry you through a lot in life. 

6) Don't remain stuck in a situation If you don't like where you are (job, home, relationship, etc) then work to get out of it! Even if you can't get out of it immediately, work at it. Plan, research, take baby steps, anything positive. Anything but wallowing in despair and negativity.

7) Expand your mind Never stop learning. Even if it's just reading a book or watching a documentary. If your exercise your brain, your mind will stay healthy a lot longer!

8) Don't be part of the herd Community is important, but don't let your community become your identity. Embrace your individuality and uniqueness!

9) Don't expect your children to give back The key word is "expect." If you treat your children as if they owe you, they will resent it, and you will resent them in turn. Give children unconditional love and care, and let go of the idea of payback.

Obviously, that's not a comprehensive list, but it's wisdom from one woman who has spent nearly 100 years walking this earth, and I think it's worth heeding.

 MTFBWY

Source: "Mistakes To NEVER Make | My Advice At 83 | Life Over 60" https://www.youtube.com/watch?thv=jrKiV7NO2a0