For what it's worth.
I think when you say 'for what it's worth', you feel that what you have to say may not make much difference, or in fact is not worth very much, but you are going to give your opinion anyway.
Context: Someone wants to buy a new house but can barely afford it.
Speaker A: 'I want to buy that house. I made an offer of £180,000, but I'm not sure I can afford the mortgage'
Speaker B: 'For what it's worth, I think your offer was too high. You should have offered £175,000'
Speaker A: 'It's too late now'.
Context: Someone has just broken up with their partner.
A: 'I broke up with Steve'
B: 'That's a shame. Why?'
A: 'He was cheating on me'
B: 'For what it's worth, I think you did the right thing'
Not sure about the second thing: 'whatever gets you through tonight'. To me it sounds like someone has to attend a social event they're not looking forward to, and 'whatever gets you through tonight' would be the thing that helps you to cope with it. For instance, drinking a lot of alcohol would 'get you through the night'.
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