At age 9 I started the clarinet. My eldest sister started the flute several years before, my middle sister started the saxophone, so the final non-double reeded woodwind instrument fitted the pattern.
At age 11 I started the saxophone. They're fairly similar, in fact parts of them use the same finger patterns to create the same notes. I also started the piano which took more brain power but soon fitted in.
At age 16 I was doing A level music so got a free music lesson with the local music service. At this time I'd already switched to private lessons given they provided better quality, so I picked up a new instrument - the cello.

The cello's wildly different to the other instruments I play. It doesn't use a reed, you can't really stand up to play it, it comes in one piece but these reasons aren't why I'm still horrendously awful at cello.
The reason is it takes a different skill set to keep the sound in tune, and unfortunately for 16 year old me, I wasn't accustomed to sounding awful.

The same thing happens in computer science - I get so used to being good at x that it's hard to accept that you're going to be bad at y for a while. It can make it hard to force yourself into doing it and there's times where I feel like I'm trying so hard to tread water, when am I going to learn to swim?

I don't really have an answer to that but I'm trying to not get ahead of myself and persevere asking the stupid questions because fixing stuff and learning is more important than panicking over who thinks you're an idiot.