What the Rav said:
Every day we start anew. It’s forbidden to think about what happened yesterday.
Yesterday, I didn’t learn, I didn’t pray, I got up at one in the afternoon, I got up at noon, I forgot to put on tefillin yesterday…
Every day is a new creation. It’s like a new reincarnation. Whatever happened yesterday is like what happened to me in a previous lifetime.
Today, I’m going to serve Hashem from scratch. I’ll get up at midnight, I’ll pray in the sunrise minyan, I’ll go to Hevron, and then I’ll learn Gemara and Shulchan Aruch for eight hours.
In doing so, I’ll rectify all the days that came before it.
We learn from Rabbi Nachman the importance of starting afresh, constantly.
Rabbenu teaches us that every day, we should try to serve Hashem like it’s the first time. New is something exciting and invigorating. If we can serve Hashem like it's the first time, then we'll be excited and invigorated.
The Rav here is also telling us some cool secrets about how to achieve this.
First, we have to completely forget about ‘how bad’ yesterday was. The yetzer hara loves to remind us about our failures, it’s one of his favourite ways to keep us far away from Hashem.
So, we need to completely forget about what happened yesterday – as if it happened in a previous lifetime. It's not for dwelling on (take it to your hisbodedut, make teshuva, finished).
Next, we need to know – and I think this is a big chiddush – that it doesn’t matter how bad I was yesterday, if I fix it today, then - it actually fixes everything! Including all the previous times when I didn’t manage to achieve this!