Any wide open lens behave like this. You need to be aware of it's strengths and weaknesses then employ them to your advantage.
When shooting people close in always try to get an AF lock on the eye so it's the sharpest in the image.
AF looks for high contrast; the wetness of the eye is offset many time by the high contrast of the subjects hair, which will throw off the AF lock.
Better cams can grab this; pro cams AF systems excell at it. So there's a little test to play with...
To get more of a spherical subject reasonably clear verses a flat object with a wide open lens you need slightly more distance than one say at f/5.6
Even with a stopped down lense this still applies to a lesser but very tangible extent.
Learn to see as the camera does... and you'll see a big improvement. Human vision is quite different; the hardware and processing power of the visual cortex is extreme.
Experiment, just a foot or two further back can make a big difference