Frustration

So the past couple nights/mornings I've been getting very frustrated with my 8 week old when she wont sleep. She's always been tough to put down, but we started getting into a groove where she would sleep 5-6 hrs without me holding her at night, it was glorious! Then she reverted back to only sleeping 1.5-3 hrs and I would suddenly get very frustrated with her, then feel bad for feeling this way towards my helpless little girl. Can anyone relate?