I find its harder to learn things that are outside my environment or academic experience. Programming languages of all types are fairly easy unless they use a different paradigm. The most recent example was the Elm language which uses functional programming but has some things I don't yet understand how they work (hidden pathways maybe).
Mathematics past the usual applied math learned as an undergrad are okay but I only remember the tricks of calculus. I trying to relearn DE, Linear Algebra, Vector Analysis but struggle with Differential Forms still trying to understand why they are so useful despite what I've read to that effect. Also with more abstract math like Sets, Group Theory, Abstract Algebra and Pointset Topology where my proofing skills were limited to Geometric proof and the sheer volume of terminology and theorems is overwhelming to my puny brain.
We do program development in a restrictive environment and so remembering how I hacked a program to get it working evades me unless I write down the changes but then I can't discern the valid changes. My solution was a frontend script to VI that saves a copy of the original code if I change it allowing me to go back later and review the specific final changes I made to get it working. A kind of senior citizen feature. It works great. Believe me. Really, its great. Great, but I digress.
I'd like to develop a learning system for seniors that can compensate for our mid-term memory loss issues but I can't remember where to start :-)