I'm mid-homework and I came upon following sentence: "Seine Mutter ist (nurse)." Should I write "die", "eine" or simply "Krankenschwester"? And why?
If you want to point at one specific nurse or there is just one then "die Krankenschwester" is the correct term. -> His mother is the nurse.
Otherwise you want to say "(eine) Krankenschwester". If you just want to say the job/profession you can omit the "eine", that is what I mean by using paratheses. -> His mother is a nurse. As far as I know it is never wrong if you don't omit it, though.
I dont know if my explanations are understandable, tell me if anything is unclear.
Shaoriko is correct, it depends on the context. Seine Mutter is Krankenschwester (no die or eine) in regular sentences if you want to say his mother is a nurse. If you want to add emphasis "die Krankenschwester."
It was the same for me, I had a streak well over a year and then I let it drop on purpose because I saw that I really just wanted my streak to stay instead of actual learning something. I "cheated" with doing easy lessons again if I wanted a break etc.
Conclusion: A streak isn't anything I want or need, but everyone is motivated differently so do what you feel is best for you.