I am finding could-be-worse-but-thankfully-it-didn't technique the best tool to kill negativity and attract abundance.
If you are trying to feel gratitude for good health, you are probably trying to focus on the benefits and good things related to your health. Here's a much stronger technique that will shift your vibrations instantly: focus on worse possible things that could have happened if your health had been taken away from you.
Please pay attention and read on to feel gratitude for your legs (a great blessing from the Creator)
Example: Instead of focusing on only the benefits of having two legs, imagine the troubles that could have come if you didn't have legs or lost them in an accident (It is common for things to get worse, so don't think you are entitled). Spend a minute or two thinking about the troubles that could have crippled your life and then shift your mind back to the reality (have a sigh of relief that your legs are intact ! thanks Lord).
With closed eyes, imagine that you have lost your legs accidentally. Now think of the troubles. Feel the sense of losing the legs ! You would not have been able to walk, jog and run. Feel the helplessness. You would have been glued to wheelchair (bring an image of a wheelchair in your mind). You would have been dependent on others for even day-to-day tasks like going to toilet, taking a shower and going to the beach. Imagine the level of pain and limitations as a handicapped person.
Now get back to the reality and look at your legs. I am sure you are now feeling genuine gratitude for your legs (something we usually take for granted and don't pay attention how important they are to us).
Apply this could-have-been-worse-but-thankfully-it-didn't technique to other areas of your life.