Not a fan of stuff going away forever, but I wished I did those things when they were current, missed out on a lot of good transmog and those lovely pandaren phoenixes.
Not playing the game enough and was ether busy looking up stuff on the internet, stacking off to watching shows and video games or just time in general.
being a bit slow levelling this toon and missed doing the bfa pre quest for the undercity bat mount
i love that mount… hope we get a reskined one soon. mabye from the monthly vault thing
When i joined the game i thought it would be fun to play as a healer, and disc priest sounded interesting with its shielding people from taking damage. So i went with a priest.
I levelled as disc, quested as disc, did dungeons and raids as disc. I had fun with the class.
Jump 6 years in to the future however and i dont do group content very often so i rarely heal, disc is no longer all that good in world content with low dps. I could always swap to shadow priest, but i really hate the visual effect of shadow form. Id much rather be able to see my character.
I made a warlock alt and ended up loving everything about it. Its way more fun for doing world content than any of the priest specs.
And when im in a dungeon or lfr, there is no stress or worries about health bars. I see the way tanks like to race through pulling everything in sight and im just relieved im not healing that.
So yeah, i found a class thats just more fun, and i dont think i ever want to heal again.
I wish warlock had a healing spec so i had to option to heal on my character, but its a small price to pay for having 2 specs i love, 1 spec i like, and a tank with me at all times.
I know that was rambly but i hope that explains it 
I should have chosen a class with a back up plan for if i ever didnt want to play that one spec. Like a shaman or monk.