Improving performance in PE

Its been slightly over a year for me in private equity having moved to the Buy Side in May last year. While things started off well, I have struggled to deliver high-quality work post the first 3/4 months with my work often having errors in addition to finding myself struggling to meet committed deadlines. While I have tried to plan better and check work, the heavy workload (2 AM/3 AM weeks) has resulted in slips to the extent that people's confidence in my work has been eroded. How would one go about trying to repair the same and also ensure the mistakes aren't repeated. To give context, prior to moving to PE, I worked for a reputed MM IB where I was a top-rated analyst.