Hi PL,
No one said it's gonna be easy, and the toughest thing to do is also the one that sounds the simplest, which is to keep looking forward and keep working.
Instead of sending encouraging words (which I feel don't work, since encouragement is temporary and they fade out on a bad day) I'll issue you a challenge instead. Keep working and keep improving, never stop.

One really useful trick when painting with a mouse (especially mechanical stuff) is hold the shift-key while using the brush/pencil/eraser-tool (in photoshop). That way the programm automatically draws a straight line between each click.

I use a Logitech mouse since I don't own a tablet.