What do you do when it feels like everything you've built for yourself in your life is crumbling?

Hi Alex, good afternoon! It is really great that you are reaching out for support at this time. Thank you so much for bringing this important question to the "Ask a Licensed Therapist" forum! It sounds like you are seeking guidance on how to  manage your recent medical diagnosis. My hope is that I can assist you in coming up with strategies to navigate this experience as well as manage the feelings that you are having at this time.

First and foremost, I realize that this must be incredibly difficult to find out that you have a genetic disease. How recently did you find out about this diagnosis? Did your primary care provider suggest that you begin to terminate your employment? It sounds like you will have no choice but to leave your job and that you anticipate that this is going to be a challenging change for you since you love working at your current job.
What do you do for work? Are you planning to take on another job at some point? Depending on where you are at in the process, you may want to connect with a therapist who specializes in career counseling as a means to figure out your next steps in your career. A career counselor should be able to assist you in developing an exit interview as a means to process this experience and reflect on your work history.

In your question, you mentioned that you feel as if your life is crumbling. Based on what you wrote, it seems like you have put in a lot of effort to build the life you want. I can imagine that the idea of not being able to live the fulfilling life that you had envisioned would be devastating, to say the least. How are you feeling about this situation? You mentioned that this diagnosis was unexpected for you. Are you feeling a sense of shock? I want to encourage you to identify your emotional experience using the feelings wheel. This resource is online and free. The feelings wheel encompasses a myriad of feelings that you can pin point in any given moment. You may be feeling more than one emotion at a time. Once you have an understanding of how you are feeling, it would be great to begin identifying as to why. These are some of the first steps in the process of developing emotion management skills. 
If you are willing to try, take some time every day to keep track of your emotions in a feelings diary. I highly recommend incorporating this into a therapeutic writing exercise. Therapeutic writing and journaling can be an incredibly powerful process technique. For more information on the benefits of journaling, check out the information from the Therapeutic Writing Institute.

As for your concerns about giving up your interests and hobbies, I can certainly understand why you would be questioning a lot of things right now. Are you open to trying out new activities as a means to replace the hobbies that you are having to give up? Take some time to check out a list of coping skills. There are many resources online that provide ideas for coping strategies. Perhaps you can try out one new coping skill each day. 
As another means to cope with this experience, I would like to encourage you to participate in art therapy interventions. The art making process can be fulfilling, healing and eye opening. As a registered art therapist, I have witnessed first hand the benefits of therapeutic art making. If you have time, I recommend that you try out the "Road of Life" directive. In this art based drawing assessment, you can draw, paint, collage or sculpt a representational road of your life. Take some time to envision a map of your past, present and future. With the art materials of your choice, you can channel your energy into your art work.
This processing technique may assist you in gaining additional insight into your experience as well as solidifying your expectations for the future. It is a possibility that you may find some solace in the art making process. For more information and ideas on the topic of art therapy, please check out the information provided by the American Art Therapy Association. Their website is: www.arttherapy.org 

You stated in your question that you are finding it difficult to accept your current situation. In order to become more familiar with the process of accepting this experience, I would like to encourage you to try out the principle of radical acceptance. This dialectical behavior therapy approach could be very beneficial for you to try. The radical acceptance strategy is considered to be a distress tolerance skill. Essentially, you can begin to practice this technique by accepting all things at all times. Acceptance has been researched and proven to be helpful in tremendous way for many individuals. One of the elemental aspects of acceptance is to commit to removing judgement about the current situation and see experiences for simply as they are.
Additionally, McMaster University has some examples of mindfulness based approaches and stress reduction strategies that are free on their website. Diaphragmatic breathing and guided visualization exercises are on this website: wellness.mcmaster.ca/your-health/mindfulness-and-relaxation/

At this time, I would like to recommend that you begin attending individual counseling sessions. In addition to attending one on one therapy sessions, you may also want to consider attending a therapy Group or a Groupinar. This will give you the opportunity to tell your experiences as well as hear from the experiences of others.

Thank you again, Alex, for taking the time to ask this essential question on the BetterHelp platform. I hope that you find my response to your question to be helpful for you in some way. I want to wish you all the best on your therapeutic journey. Take good care and have a nice day.