I had a nasty lung infection in 2017, I couldn't cycle, or walk more than a few yards. It was so bad my GP suspected cancer and off I went (13 days later) for an appointment with the specialist. He ordered a bunch of tests which eventually decided it was merely an infection (6 weeks of sample culture on my sputum identified the bug and which antibiotic would kill it.) On my first real ride on my trike 10 months after the first indication of illness, I stopped at my halfway point, got off the trike, looked around and sobbed, uncontrollably! Relief does that to you.