Light brings Joy
I remember the very first winter after I became an accountant. I would leave home while it was still dark. Sit in an office in artificial light until lunch time. Pop out for a sandwich, bring it back to my desk, eat it there. Then by the time I left at 5 or 6 it was already dark. After a couple of months I began to realise this was getting me down. I realised that at lunch I had to go outside and walk around and get some sunlight - because I could not cope with a whole day without seeing the sun.
The light of Christ brings unspeakable joy to those trudging along in darkness.