frustrated and asking for opinion

I left my previous company and came to this new company which is closer to home and paid very well 4 months ago.

Unexpected, the work load and quality of this new place is very high, aggressive, and demanding , I hardly feel I could handle, even though I tried the best I could , my manager is still disappointed at my performance. So I must've shown some impatience and frustration as well .

He said they hired me with high expectation as well as highest salary a developer could have (developer 3 LEVEL and nobody in this company as developer is paid as high as I do). .... and I didn't show that type of performance. He wants me to think about this --- Do I still want this job , then in this case I need to improve my performance, he even has a plan for that , which I DON'T know that yet, it might be ridiculously high standard just to boost me out...... otherwise, he would let HR give me termination and try to put up package, but since I'VE been with them for only 4 months, not sure how much I could get, but again that's HR thing.


Now I face the reality and just think about my next step/plan...one of my friend told me in my case ,I won't get too much package...but instead I should try to negotiate a maybe month-long improvement agreement to get a chance of re-evaluation from the manager...if after one month, he thinks I still didn't perform well , then tell him I quit instead of having a record of  laid-off by the company which has negative impact on my future job seeking. ( in this case I give up the separation package),  

This sounds like not a bad idea, what do you think? I really think I need to move on and don't think this place fits me well, but I want to find the next job ASAP, even willing to take lower salary.


thanks!