Regressing in work quality

For some context, my first year went pretty well - sure, there was a steep learning curve and I made mistakes along the way, but I quickly improved and learned to not repeat those mistakes. I get along well with all levels of my team, from my fellow analysts all the way up to the Directors and MDs. I was really happy with my year-end reviews this past summer as well. 

However, I can't explain why - but this week has been really tough for me. I've had to juggle even more things than usual, and I've been put in charge of onboarding our new joiners so that's taking up a good bit of time as well.

For a client deck this week, I kept making mistakes that I normally would not make, which concerns me. I got chewed out for it, which is to be expected. I can't explain really why this change in work quality is happening - mental health is solid, and there aren't too many outside distractions. I think it's mainly that I'm being stretched too thin and have to keep track of so many different things, so sometimes other things will fall through the cracks. 

Does anyone have advice to rebound from this? My self esteem is not the best now, and I'm getting extra paranoid and worried that this will happen again in the future. I do try to double and triple check everything, but when under such time crunches and when working with very demanding (sometimes unreasonable) people, it can be hard to make sure everything is perfect.