Ask HN: Developer's Block. Please Advice

I am facing something that every developer does on a number of occassions in their careers i.e. a challenging and an insurmountable problem to solve , build and deliver a complex feature with near infinite user scenarios and edge cases. This is not the very first time in my 5 years plus career that I am facing this situation. However , this time and probably the very first time I feel paralyzed and almost defeated by this feature that am trying to build since almost a week (including the weekend). Every solution I build fails to achieve one or more core scenarios or unit tests. I am almost at the end of my estimated schedule without a stable feature that I am to deliver and demo this week to end users. I am extremely passionate about the software development craft (with a big thanks to the HN community for that!). I love solving such problems and have done so from the very moment I took my first software dev role right out of college. I really don't know why am feeling unusually stressed out due to this one seemingly unconquerable feature. Inspite of having put in extra hours at work I see no perfect solution on the horizon . What makes me even more disappointed in myself is that as a senior developer I am unable to solve this , and I aspire to work in companies like Microsoft , Amazon etc. Seeking advice from this wonderful community. How do I deal with this and what are some steps I could follow to get through this without losing my mind? What can I do to prevent myself from having a nervous breakdown like this in future? How did you deal with such situations in your career and get out of it still standing tall? Thanks!