Very, very helpful. For me it has been key.
I don't know if you like YouTube videos. If so you might find this useful (Marsha Linehan, who developed DBT, explaining how it came about):
DBT was originally developed for people with a diagnosis of Borderline Personality Disorder (BPD), but it's increasingly used for a whole range of things. I don't have a BPD diagnosis but I find DBT and mindfulness really helpful for what I am diagnosed with - PTSD, obsessive compulsive disorder and anxiety.
The skills have helped me through suicidal ideation and unhealthy coping methods (common to both BPD and to PTSD). They have also helped me to work towards a better life. I don't know if you're familiar with the DBT "strapline", which is "Building a life worth living". I did not have a life worth living and I didn't see it as a possibility, but DBT has given me some hope for that, and some understanding of what that might mean.
To me, DBT and mindfulness are good for severe issues and they're also just good mental health, good coping and good interaction skills. I think they should teach them to everyone in (high) school!
I did find some concepts difficult at first, especially radical acceptance and mindfulness. If the first explanation you get doesn't explain it for you, keep looking/asking for more explanation, and also be willing to only partially understand it but give it a go anyway. I found that understanding it came along with trying to do it.
Something I really like about DBT is that you can approach it at different levels. When I was barely functioning and using very unhealthy coping methods, I could still make a list of things to distract me and things to soothe me. At that point, they were small and fragile lists but they were something. I could do them, and I could use them. That was the foundation for getting to a point of much better functioning and much healthier coping. Now, my lists are much more ambitious and expansive.
I'm so glad for you that your therapist has suggested this. I've had several turning points in healing, and DBT/mindfulness skills have definitely been one of them.