Fun,
What is the fertilizing routine?
Is composted manure ever applied around the roots and it is mulched?
Depleted soil could account for lack of vigor.

I notice my star jasmine leaves droopy from time to time, but never ends up dead. After I water it , the next day, it will look normal again. mine is in the pot, I always thoughtthis maybe something to do the temperature.

Butterfly4u, Fertilizing routine? Umm...none...maybe that's the problem. No mulch. Can I use a time release nitrogen fertilizer that's for house plants?

Olympia_Gardener, I had the gardener trim the plant back as it was quite heavy with blooms. That seems to have perked up the leaves. Maybe it was just too much foliage or maybe it needs fertilizer as Butterfly4u suggested.

Thank you both for your help.

I had the same experience as Olympia Gardener, one I grew in a pot would always go limp during the afternoon but after watering it would perk back up a few hours later. But I never notice the ones in the ground doing this (even in poorly-watered landscaping).

Fun2be,
You had stated you had it for years, so I thought I would ask you waht you fed it.
I put composted manure in the soil every spring, then renew the mulch to help hold the moisture in when it starts to get hot.
You can add any plant food to the soil down by the roots, mix it in and water it. Then add a litle mulch around roots.
Then next spring do it again.
I have found Osmocote is really good.
Soil looses it's "good stuff" after years of having a plant "taking" from the soil. Replenishing the soil by adding compost is always good for the plant.
By the way, it's beautiful!