How does one increase their 'window of tolerance'

The reason I say this is I am diagnosed with DID, I recently went through 2 more traumatic events recently and for whatever reason these trauma's more than anything cause me to keep splitting and splitting more alters, which is horrifying to me enough as it with the traumatic things happening in my life already.

My therapist told me that I needed to take things easy and try to raise my 'window of tolerance' as much as I can because they were understandably saying that all these new alters are forming because I can't handle what's going on outside of therapy anymore, and needed someone else to handle it for me, hence the new alters.

How does one do so? It seems so vague, does it refer to me doing things that are just healthy for myself/mental health in general? I really don't want to keep creating more parts because my brain thinks I can't handle it, I want to handle things myself.