She dwelt on the miserable days she spent there.

Poor though they were, they didn't worry about their future.

He dwells on his past failures.

He always worries about minor points.

Don't be so glum about it. Life has its ups and downs.

One should not lament over past mistakes too long.

Don't trouble about small things.

He grieved over his failures.

I advised him not to grieve over the past.

I wouldn't have worried about that.

It is no use crying over spilt milk, as the proverb says.

Don't worry about giving a speech at the wedding; you can just wing it when you get there.

Don't dwell on your past mistakes!

Don't dwell on your past failures.

Don't worry about the past.

What's eating you?

Do your best and don't worry.

You just messed up once. You don't need to agonize over it.

Don't worry about such a trivial problem.

You need not fret over such trifles.