How do I reduce a charity pledge when my name is already on the supporters' wall?

A volunteer thanked me by name at the community meeting for my $25 monthly pledge. I smiled, then spent the walk home wondering how to take it back.

When I pledged six months ago, I usually had around $100 left after the expenses and savings I'd planned. A new regular family cost has reduced that to about $40. I can still pay the $25, but it now leaves very little room for anything else. The charity matters to me; its local transport sessions helped someone in my family.

I could give $10 instead. That wouldn't close a hole in my budget completely, but it would make a difference. I haven't contacted the charity because I feel as though the public thank-you turned a monthly amount into a statement about who I am.

Would you explain the changed budget, simply request a lower pledge through whatever process they use, or keep paying until the anniversary of the original promise? I want my help to be sustainable without making a small donation feel like a public withdrawal of support.