Self control and practice...
If you are working in that type of hood, you are relying on sterile air blowing any contaminant out of the workspace (at your face, hands, and body). To be effective, there should be little to no obstruction, which makes turbulence, which sends junk flying all over the place (even the junk you can't see). So, keep your workspace uncluttered. Don't put possibly contaminated things (your hands, tools, etc) behind an open flask. Just work on being aware of how the hood works, and where your hands are. You will get used to it.
I'm used to another kind of hood, which blows a sheet of air down vertically, isolating the interior of the hood from the exterior. So that is where i'm most comfortable. If I had time to use a hood, anyway...