I offer my assistance whenever I can

Let me know if you need anything is the most common offer and the least usable one. It hands the work back: now the person in trouble has to identify a need, rank it, and ask a favour while feeling like a burden.

The offers that get accepted are already decided. I'm at the shops, what do you want. I'll take the bins out Thursday. I'm outside.

It's a smaller kindness to make and a much larger one to receive, because it removes the asking — and asking is precisely the thing people lose the ability to do in the weeks when they need most.