Once the elements of a transformation start supporting each other the transformation starts to feel like it will take root. You may still feel some inertia, fakeness, and conflict between the old and new you, but decreasingly.
Examples of elements supporting each other include

• After starting a new hobby (behavior) you start meeting others who do the same hobby
• People compliment you on losing weight
• People you meet in new circles of friends or colleagues have mutual friends
• Confirmation biases start reinforcing new beliefs

and so on.
You also start feeling reward from new cycles as the elements in them resonate with each other. That reward means you decreasingly need to use willpower.
Once you start feeling some reward, you generally don’t doubt if the transformation will work out at all, as described in the caveat for stage 1.
By this stage, while you could slide back if you let up and had attachments to the old you, completing the transformation is usually a matter of time.