I sure hear you about the anxiety with treatment. It's a tough diagnosis and a lot of very weird treatment, with lots to learn before we can feel like we're in control again. Sending you cyber-((((hugs!)))) that I hope will at least let you know you're not alone!
Besides drinking plenty of water (which is a great idea and will certainly help--keep it up!) you can also pause throughout the day and take a few deep, abdominal breaths. As though you were blowing soap bubbles, y'know? (In fact, go ahead and get a bottle of bubble soap if you'd like, and blow a few throughout the day.
) The deep breaths help to stimulate the biggest lymph vessel in your body, which runs past your diaphragm and gets an extra boost whenever you breathe deeply. But deep breathing also helps calm you, so it does double duty.
I too found lymphedema wrapping anxiety-producing at first -- we sure aren't used to lugging around a Michelin-man limb! What helped me was to distract myself as much as possible with absorbing things I liked to do -- in my case Sudoku and crossword puzzles and funny rented movies. Hopefully the anxeity will pass as you learn to deal with the LE yourself and take charge of your own self-care. For me the anxiety made it hard to concentrate, so I kept a list of questions to ask my therapist and wrote down the answers she gave me so I could remember later. I took my husband with me to therapy, too, to help me hear and remember everything I had to learn.
Prayers, Wendy, for calm and for at least a few moments of real delight every day, in spite of it all!