“Well, what's done is done, I guess. ”
Your daughter dropped her phone and broke the screen, so you have to get it fixed. At first you were angry, so you yelled at her. Now you've calmed down.
Well, what's done is done, I guess.
You can end your sentence with "...I guess" when you're either not very sure about something:
A: It's not working.
B: You have to have a password, I guess.
You can also use this phrase when you're not happy about something:
I'll stay here and keep working, I guess.
Another phrase that you can use in this situation is "I suppose," which is a little more formal:
A: Is it OK if I send you the payment online?
B: Yeah, I suppose.
You use "well" to change the topic or the tone of a conversation:
A: How are your classes going?
B: Not too well, to be honest. Calculus is kicking my butt.
B: Yeah, I'll try. Hey, have you talked to Priscilla lately?
You can also use "well" to signal the end of a conversation. For example, you might say this after talking to someone who's just returned to work from maternity leave:
"What's done is done" means that you can't change something. For example, if you break something that can't be fixed, you can sigh and say:
Oh well. What's done is done.
You could also say this if you bought something that you're not happy with but you can't return it.
When you say "what's done is done" it sounds like you're not very happy with the situation, but you're starting to calm down and accept it.