Here is my revised version of my first self portrait and my second self portrait.
The main difference between the way I went about the two self portraits is that the second one (on the right) was done from photo reference and the first from life. It is so much easier this way as you don't have to deal with the subject moving or the light changing, both of which were problems I had with my first attempt. I had two light sources for the first portrait, the angle poise lamp on my desk and a window about 8ft to my right. I started the portrait just after lunch and finished a few hours later. As it was winter the sun went down and changed the lighting in the room and I really struggled to make sense of the changes. Also, like a complete plum I managed to move the lamp half way through which didn't help! Other ways that working from a photo have helped include the fact that you don't have to try and hold the same expression for ages (I chose a deadpan approach to the first one for this very reason) and you can zoom in to check details. Anyway, the end result is that as a self portrait the second one works alot better.
The image on the left is a revised version of the first portrait with a few changes made based on observations I made during the second one. Noteably I have changed the shape of the chin and a little of the structure of the cheeks and temples. Also the mouth is narrower and wider. I didn't want to tinker too much but even these little changes which I did in about 10 minutes make a big difference.
I will continue to do these and will be working both from life and photo ref, the ultimate aim being to become as proficient in life as from photo's.