My geranium sanguineum's leaves have become dry and shriveled, it is still flowering but looks really sad.

Well its usually drought, but surely not, the weather we've been having! Can you see new growth coming in the middle of the plant up from the ground? At this time of year, new growth usually starts in the centre, and you just cut off the long previously flowered growths back to ground level and, in your case, the growths that are brown and shrivelled. The new growth takes over and gives you more flowers.

If it is near a tree then the ground possibly is dry, have a scrape at the soil Loubielou and see. Ground near trees and hedges can be dry even when it has been raining for days.

Definately drought - Moon Grower is correct. Cherries are heavy feeders in every respect, which is why they disrupt ground so much, and are viewed with great fear within 10 metres of any structure.
Solution?
Move it and water it.

There you go...