A high guard has pros and cons.
First off, the pros:
- Protects your eyes
- Protects most of your face
And now, the cons:
- may obstruct vision
- May not protect your mouth
There's more, but those are just some examples. Personally, I prefer to take a stance that allows me to block just below my eyes so I can see, but if I see them coming, I can quickly move my hands up. Unfortunately, there may not always be enough time to do so, and you may have to take a hit.
Me being only a white belt and being involved in martial arts for a full 3 weeks now, I don't have much experience, but I have sparred before, and this strategy has saved me from losing a few times.
But you don't have to listen to a noob like me if you don't want to :)
for future readers: look at the age of this post :)