I couldn’t resist swimming in this Olympic-size swimming pool on Fuerteventura a few weeks ago.
Although the water was really cold, I swam for more than 30 minutes. 
I didn’t wear my wetsuit which was a mistake. I started coughing the next day. I mostly ignored the symptoms while hiking on Gran Canaria in the sun. That was another mistake.
Getting really sick
I felt really unfit when I met my friends for lunch in Puerto de la Cruz on Tenerife. When I sat on the couch at the terrace of their AirBnB, my body forced me to rest by literally knocking me out. I fell asleep in the afternoon and woke up with a high fever in the evening. After sleeping for almost fourteen hours, the fever was gone.
One of my friends and I went to the beach. The sun felt really bad, so I lay down in the shade behind some palm trees. We met the others for lunch in San Cristóbal de La Laguna where my body started resisting again. I wasn’t able to join my friends exploring the town, so I walked back to my van where I slept for another fourteen hours with a high fever.
Bummer! I had taken the whole week off to spend time with my friends who only stayed for five days. Instead of joining my friends exploring the island and enjoying the local food and drinks, I spent four days in bed with a fever. 
I had basically traded 30 minutes of swimming for a week of vacation with my friends. What a bad deal!
Resting in the woods
By the time my friends left, the fever was finally gone. I still felt really exhausted, though. I bought garlic, ginger, lemons and a bunch of other vegetables and fruits and drove to a quiet recreational area in the woods in front of the Teide volcano to get some rest.
I didn’t do anything but sleeping, eating or drinking tea in my bed. 
After spending three days at that peaceful spot, I started feeling better. Nevertheless, I was still too weak to ride my mountain-bike or hike the volcano, so I decided to take the ferry to El Hierro.
Eventually, I’ll come back to climb the peak of Europe’s highest volcano (3718 meters). 
Until then, I’ll take it easy and get back to energy on the smallest and least populous of the Canary Islands.