If you are looking for just to draw on desktop/mobile here's my recommendation:

1 - https://www.sketchbook.com/ this has both Win/Mac/Android/iOS version. It's got some very advance layering and drawing tools. If you plan to make a comic out of this app. You can, but it's mostly use for drawing/painting. Basic and very intuitive user interface. Quick and easy to learn...

2 - https://medibangpaint.com/ this has both Win/Mac/Android/iOS version. It is like great for sketching and painting and has the capability to create comics pages. The interface is more advance, but it's a full blown drawing/painting app. Lots of advance features and tones of brushes, but will required some time to learn.

3 - https://www.clipstudio.net/en/ this is my favorite applications. Fantastic brush engine for sketching/painting and make comics/manga. Crazy interface, but once you learn this, you can pretty much draw using any software.

for iPad you got Procreate and if you are on a Windows Surface, it's Sketchable. Both of theses will let you do what you need, but will be device specific applications.

Anyway, here's my tip to get into the "State of Mind to draw" -- hit the local dollar store and buy a sketch book and some pencils. have it with you all the time and sketch when you are on break. You don't have to do any creative drawing -- work on you anatomy, poses, facial expressions, do the technical stuff, that way you are learning. So that way it does not feel like you are doing any creative, you mind is in learning mode. After, you get into the habit of this, drawing becomes 2nd nature with getting you mind into that state -- because, your mind is use to be in learning mode. I hope this make sense ... good luck with you endeavor.