what is magick? there are many definitions, so it's best to research and reflect, then make your own definition. magick is the natural neutral energy found in everything that we can tap into and direct on a path to bring a desired change. these changes cannot contradict nature, so if a human cannot do something [fly, teleport, shapeshift] a spell won't make it real. magick effects the energy around a situation to help you reach your goal [a love spell effects your vibrational energy to attract someone similar]
how to tell if your abilities have grown, through practice you should notice subtle differences, like starting out i couldn't sense energy, as i've practice i can feel energy when i touch certain objects [say a friends tarot deck, or when shopping for crystals]
LunarLady, a metric is a means of measuring something. As you learn, study, follow a tradition (or not follow one, and remain eclectic), you means of measuring progress is success.
What do I mean? Here are some rather arbitrary examples:
If your meditation has increased from five minutes to thirty, you have improved your ability to meditate.
If you used to struggle with casting a circle, and now it is second nature, you have improved in this way as well.
If you used to lie down attempting astral projection, giving up after a while; eventually you realized you were reaching the so-called vibrational state, and you could feel your arms moving at your will, even though you know you had not moved your body physically, that is progress. If you find yourself able to slip into a trance state such that you can bound off on an astral journey in just a few minutes, congratulations: You have made a lot of progress.
If you are more certain when you would like to do a working or cast a spell to gain some result, that is growth in knowledge and perhaps wisdom. If your workings are successful more often, that is another example of growth.
Growth in magic is not that everything necessarily happens more easily all at the same time. Each practice you take on is a different, although some are related, skill.
I agree the more you practice the better and more confident you become. They don't call it practicing magick for nothing.
You definitely will notice a difference. Sometimes It takes a while, just try to learn something new every day. Then you will have that Ah Ha! moment. Magick is like any other skill, it take 10 thousand hours to master a skill.