OK let's cut through the BS. Edge is one thing and one thing only: positive expectation. If you have it, you can be a successful (aka long-term profitable) trader. Notice I said 'can', not 'will'. Edge alone isn't enough. You also need good money management, which is best exemplified as good position sizing.
Without edge, all the best money management in the universe won't save your trading account. We see this easily in the simple examples of most casino games, where the house always has the edge (positive expectation) and the <s>suckers</s> gamblers are trying and failing to martingale, anti-martingale or otherwise enchant a path to success. Some get lucky in the short run, all fail in the long run.
Here's why the OP fails to grasp the concept of edge. Say a trader does all the things in the first post (proper diet, proper exercise and rest, etc.) and as a result he comes across a strategy with permanent positive expectation. Great, all those things contributed to his success so he might think they were all part of his edge. Now he passes his strategy on to his son. Does the son now have an edge in the market? Of course he does. He has a trading strategy with permanent positive expectation. Did he have to go through the whole proper rest, etc. routine to get it? No he just needed to be a member of the Lucky Sperm club: he had a dad who was willing to give him dear old dad's successful trading plan.
The kid has an edge but he didn't have to work for it like dad did. So clearly edge is something different from the process used to acquire it. Edge is the destination, not the journey. Yes most of us have to work for it to get it, but don't confuse processes with results.