Hello, do you know any good poems about growing old, and regretting, in particular, having regrets about lost love? Also, some poems about the joy and virtue of youth?
I used to read a lot of poems for AP literature, and I enjoyed them a lot, but since then, I have never read one 
Google is not really helpful for this.
I only found one: Maud Muller
“Memory” song is also a good one
Is this homework help?
The Love Song of J Alfred Prufrock
IF this is HOMEWORK, a big hint is that SONGS are generally poems and there are countless songs about lost loves and growing old.
Oh no this is not homework
HImom–Like this one? https://www.youtube.com/watch?v=kmmPFrkuPq0
Parents probably remember it. Even when it came out in the 80s, it made me sad.
Sonnet 29 from Fatal Interview by Edna St Vincent Millay. It’s about enjoying youth & old age. I especially like the last 2 lines 
It’s the second one on this website: http://www.violafair.com/poetry/millay/millayfatal5.htm
(Starts with “Heart, have no pity…”)
Yup, Prufrock came to my mind immediately.
Wm. Butler Yeats, “When You Are Old”
“On Turning Ten” by Billy Collins
Maybe try Sara Teasdale.
I think that Fields of Gold speaks to your themes, OP. It was originally done by Sting, but Eva Cassidy’s cover is one of the most poignant songs I’ve ever heard.
Jim Coerce, “Time in a Bottle” is a very bittersweet song–love song but also about passage of time.
Jim Croce.
Not so much for OP, but one of my favorite growing old songs : https://www.youtube.com/watch?v=Ul2hSba5pOs
On the poetry front, what about “To the Virgins, to Make Much of Time” by Roger Herrick? OK, that’s all from me.
TO THE VIRGINS, TO MAKE MUCH OF TIME.
by Robert Herrick
1891
GATHER ye rosebuds while ye may,
Old time is still a-flying :
And this same flower that smiles to-day
To-morrow will be dying.
The glorious lamp of heaven, the sun,
The higher he’s a-getting,
The sooner will his race be run,
And nearer he’s to setting.
That age is best which is the first,
When youth and blood are warmer ;
But being spent, the worse, and worst
Times still succeed the former.
Then be not coy, but use your time,
And while ye may go marry :
For having lost but once your prime
You may for ever tarry.
“Tithonus” by Tennyson.
Not a big Tennyson fan overall, but this is a very poignant poem–the speaker has been granted immortal life, but not immortal youth, by a god, and now just wishes to die, but cannot.
For a very large selection of poems on this theme, download the Poetry Foundation app. You can sort the poems by theme and mood. Or you can spin the wheel and get random choices. There are thousands of classic and contemporary poems, some very well known and others obscure. It is a very fun app and the answer to questions like this.