At this time of year most plants will shed a few leaves after they turn brown, especially when they have just been transplanted.
Overwatering is more likely to kill a plant than anything else - let it settle in and I'm sure that next year you will have a healthy plant.
Plants are pretty tough, they've been around a long time! We tend to think that they need our help constantly, but they can manage for themselves - most of the time.

Good luck!

I'm wondering whether you've planted it in the ground or whether it's in a pot. If you planted in the ground during summer, it'll be a water problem. When you say you give it a good water, that should mean a whole large watering can full poured gently round the base, preferably without the rose on the can, daily, as its in trouble. The best time for planting is actually Autumn, when the plant has a chance to settle in and start to put out a good root system so it can seek out its own water - if you plant during summer, then you do need to ensure it gets a good soak frequently. You cannot overwater because any excess will simply drain away. If you're not sure that's the problem, and the plant hasn't been in the ground longer than a few months, dig it up and inspect the rootball - if its bone dry or dry, then any watering you've done simply hasn't reached the rootball. Soak thoroughly and then replant.

Once a shrub or tree has been in the ground for two years, it should withstand short periods of drought withoout your having to water at all.

Thank you for your help