If you are running software that's using a game-engine, it's possible that the mouse movements are too sensitve to navigate properly. This is often the case when you can "walk around" in a 3D model.
Herefor a simple setting can be changed in the Citrix Receiver Preferences.
Note that this option is only available for the Citrix Receiver, not for the HTML5 client.
Click the little arrow at the top of your screen and select "Preferences".
Select the tab "Connections" in the Citrix Receiver Preferences window and check the box to use the relative mouse.
Click on "Apply" (and/or "OK") and test if the mouse movements are optimized.