I was first introduced to this form of psychotherapy through a Philosopher’s Note on Dr. Russ Harris' book The Happiness Trap.
ACT stands for Acceptance and Commitment Therapy, which has 6 core processes:
Acceptance
Cognitive Diffusion
Being Present
Self as Context
Values
Committed Action
POWER ACRONYM 4: A.C.T.
Each process of ACT is a scientifically sound approach for mastering thoughts, managing feelings and controlling impulses.
I'll let the links I provided above serve as proper introductions for your continued reading.
Power Acronym Daily
366 Acronyms to encourage, enrich, and empower.