Thanks for changing the title.
a) securing your bike - rarely leave the bike unattended and at home always in a locked garage
b) maintenance - I enjoy tinkering so not really a problem either
c) lights - Riding in the dark is quite exhilarating, especially with modern lights. The old ever ready lights were a little challenging, to get home before they ran out of life.
or something else??
So for me - something else.
When actually riding, weather, hills and wind all make it harder, but this is all part of cycling. I think the hardest part of cycling for me is when I have had a bit of a break, due to family/work commitments and the "week off", slips into two or three, then it is "month off" and then gets worse. Getting back into a routine after a longish break is the hardest thing for me.
Good luck with your project.