Great to see that you have reconnected with your partner and that he is working on building healthy habits. Gaining structure and control in your life is something many of us strive to do.
When someone is working a mental health issue, the journey in healing can go through many of these steps including rest, therapy, doing exercises (or practicing new skills), and then regaining strength and confidence. This healing can take time.
The journey that your partner is on may have some areas where he has to do some of these steps in his own time, and in his own way. You being there cheering him on and supporting him is a really important role.
As far as your questions:
1. Is it normal to feel so stressed out and that you need to gain back structure and control and if so, why?
This experience is different for every person but feeling out of control and not having structure can make some people feel vulnerable. Working on regaining a sense of control and having goals and structure in your life can take time and persistence. Every person has a different level of which they need control and structure in their life.
2. How can a person learn effectively to let things slide without worrying so much and stressing?
As I mentioned before, it can take time to learn strategies on how to manage worry and stress. It comes with support, skill, and practice. Some people have experiences that occurred long ago and these experiences can resurface which can interfere with this process. Sometimes people work with a therapist to unravel these past experiences which can offer self reflection and help move forward in healing.
It is normal to want to take away pain from a person you love. Gaining an understanding of someone who is learning to understand themselves can take time and patience. Like I said in my previous post to you, often focusing on your own resilience and strength can be one of the most helpful things to do.
Wishing you the best possible outcome,