Which advice would you give to someone who has just been diagnosed with Porphyria?

Do a lot of research, talk to people with the disease, and then decide what works for you. Listen to your body and communicate with your medical professionals. Try to always go to the same hospital and see the same doctors. Porphyria is a difficult disease to explain to medical professionals who have no idea what it is so stick to the professionals who know about it if you can.

Listen to the doctor. When I was first diagnosed and for many years after, I decided to fight or ignore the disease. This has cost me dearly because I now look much higher older than I am because of skin damage and I have even constant acute attacks

TO STAY CALM, YOU CAN LIVE A LONG LIFE WITH THIS DISEAS BEING CAREFUL WITH ALL THE TRIGGERS.

Learn as much as you can about the condition, ask questions, get involved with your medical team and work together to set up a management plan for your treatment and health. Research, research and more research. No two people are alike with Porphyria, you may react differently to someone else with the disease.

Find support groups and join these, this can be an isolating disease because its misunderstood and not much is known about it. You will find it easier to cope when you know you aren't alone.
Help to spread awareness, the more people are aware of this disease and its implications the better understood it will be.
The mental aspect can be devastating, make sure you understand the aspects of the disease and be aware of the triggers.