If you have a serious and/or chronic health condition, you inevitably encounter some bad days. Sometimes it can be frustrating, overwhelming, maddening, and feel like body betrayal. Get angry, feel sad – it’s ok, and totally normal, to have those feelings. I’d probably give you side eye if you were positive all the time. 
But try not to stay in that space longer than you need to. Remember to show yourself compassion. Illness is something you are experiencing and not who you are. You don’t have to like it, but you do need to accept that it is what it is in this moment. Try and shift your thoughts and find things you are grateful for – even if they are small – and build from there. Gratitude is one of my favorite practices. It may seem forced at first, but If you stick with it, over time it really shifts your perspective….❤️
https://www.healthline.com/health/chronic-illness-self-love-on-bad-days#1