How to sequence better while cooking
I actually routinely peel thing 2 while thing 1 is frying. To me the key is to work out your critical path. But you don't have to plan as I do. Just work out what your goal is:


get everything done in the least time possible
get everything done as calmly as possible
make sure nothing burns, dries out, overcooks, or cools and gets gluey


Say you want to make a piece of panfried meat (steak, chop, chicken etc) that needs to rest, along with mashed potatoes and some steamed veggies. So work out all the steps and how long they take:


sear meat 3 min each side, 10 min in oven (oh ooh, need to preheat oven), rest 10 min
peel potatoes 5 min (or however long you need), water come to boil 10 min, boil 10 min, mash 1 min
prep veggies 5 min, heat up steaming water 5 min, steam 5 min


(You can adjust all these numbers of course.)

Now you can sort it out into order so that you take as little time as possible and end up done at the same time.


dinner - 26 minutes: start searing steak. Preheat oven.
put potato water on to boil
peel potatoes (partway through, turn steak)
should be about dinner - 20 minutes now. Put steak in oven.
wait 5 minutes (tidy up?)
dinner - 15 minutes put potatoes into water
turn on steaming water
prep veggies
dinner - 10 minutes, steak out to rest
dinner - 5 minutes, put veggies into steam
dinner - 1 minute, mash potatoes, put into serving bowl, put veg into serving bowl, put steak onto serving plate, dinner is ready


The exact order will be different every time but you work it out by finding the longest chain and starting that first. For each thing you want to end up serving, you need to work back the steps to get you there and therefore when you want to start that chain. Keep in mind that an oven can preheat or a pot can boil for a few extra minutes without consequences.

Now this approach keeps the overall time the lowest and gets it all on the table at once. But you might find that too stressy. So you could do it like this:


preheat oven
peel potatoes and put them in a pan of cold water.
prep the veggies and put them in the cold steamer.
pan fry the steak, focusing on nothing else for 6 minutes
put the steak in the oven
turn the heat on under the potatoes
after 10 minutes, take the steak out of the oven to rest
turn the heat on under the steaming veg
after 10 minutes, everything should be ready


This takes 10 minutes longer because you "get your mise en place together" (that is do all the peeling and prepping) before you do anything else. But it spares you doing two things at once, and if your peeling takes 7 minutes instead of 5, all that happens is you eat a little later, you don't throw other timings off because you haven't started anything else yet. 

It doesn't matter which of these approaches you take, you can still work out the order and the times when you just need to wait for a bit. As you get faster at prepping and more confident in your prep time, you may naturally start to take a more overlapping approach.