The biggest improvement I've experienced since going full-time as trainer/consultant is not a technical improvement. It is that I've learned to deliver under all kinds of conditions. I have become part of my tools. I have learned to train a class full of noobs, a class full of experts and a mixed class. I have learned to teach the same content in 4 days, 3 days, 2 days, 1 day and in 4 hrs. I have been booked a year in advance, months in advance, weeks in advance, days in advance, just hours to the training and even after the training has started with the original trainer suddenly not available. I've learned to train people who don't seem to want the training and people who don't want the training to end. I've learned to teach in all kinds of setting/environment, from one-on-one in my living room to online over skype/teamviewer/video-recording to a class of over 30 in one room. And much more than my technical skills, it is my skill to deliver that has been my main competitive edge.
I am just like the Excel software tool I use for the teaching.
In the beginning I used to feel sick after every two days training class. It was physically draining to talk, teach and stand for 8 hours a day and two straight days. Now I train 5, 4 straight days and don't feel sick.
And this is just for the training aspect. It's also similar for the consulting aspect. Sometimes, it looks like I was designed to do this very work (actual saying of some of my training participants). I sometimes do it on autopilot. It's like a carpenter whose muscles and brain have become wired efficiently for furniture making. Like a painter who has become of his own master tool.
The work does indeed shape one.