I didn't have any stability issues starting out on a mountain bike with wide slicks. Shifting wasn't a problem then because the shifters on this old bike had numbers on them. Going clipless was more of an issue because I didn't take the time to practice and figure out which foot to clip out on. I fell over many times, I'm embarrassed to say, and at least once took another rider down with me

. When I got my road bike, I recall the shifting learning curve being rather great. I have Campy shifters, and I had a hard time remembering which did what. I threw chains going uphill. I didn't downshift before stopping. Then I started to ride behind DH and mimicked his shifting and cadence. That helped. Putting my bike on a trainer and WATCHING what each lever did was probably the thing that helped most. After awhile - like driving a car - it became second nature. I still look down at my rear cogs sometimes to see where I am, but most of the time I just know where I am by the way the bike's handling. It all takes time and practice.