Yea luck comes and goes. Missing an easy chance is not bad luck, and the highlights of this morning's game suggest that Newcastle could've scored more.
However the area where I think you have had very rotten luck is in the forwards.
With Lukaku and Sanchez essentially being replaced by young guys looking to cut their teeth, it was crucial that Martial, Rashford and Lingard stayed fit and played well. But that hasn't happened with any of them. Now you're needing to rely on output from the likes of James and Greenwood which is harsh given their ages. Mata sounds like he's been very disappointing this season too.
Again, it's not unlucky the situation we find ourselves in with our forwards. We shipped two international strikers out and didn't replace them and this exact situation (relying on Rashford, James and Greenwood) was inevitable.