Why do I always have trouble with grep?

I’ve been using Linux since the mid 1990s. I’m comfortable on the command line However when it comes to grep, I use it…it works. I document it. Later I use it again…it doesn’t work. For example I documented: [ON [9/22/2018] THE FOLLOWING WORKS!!!!]grep “using” -n /home/bill/MyStuff/Python3/*.py < This seems to work best [gives me line/line …