Appropriate goal setting is very difficult.

Two components which can be measured and could be attributed to an improvement in technique are punch velocity and punch force. Although these aren't indicators of your overall technical improvement.

Just to add to what Adam rightly posted. A good coach is invaluable, giving direct feedback on your performances and using video analysis to point out the things you're doing right.

Setting goals related to how well you do in competition would be the most reliable indicator of overall improvement, if you achieve them.