I try and avoid 'Unlucky' !   Very often, something is not unlucky, something requires correcting. Praise the effort & intention, but then ask "what could you have done differently?" 

One of my go to phrases also, "can your feet see the ball?"  - I find this is a great way to show player (of any age) the importance of being in a position to receive the ball. 

Dexter Davidson said:

can your feet see the ball

Really like that one!

You can have that for free Stephen!   

I use this with little Mini-Kickers, all the way through to my senior side!   Very simple phrase which gives a lot of information. 

Yes, much better than are you available or are you giving a passing lane etc. Thanks Dexter!