No matter how many wins you have and no matter how large they are, multiplying any string of numbers no matter how large with one zero, gives you zero.
Bad stuff happens way more often than anyone thinks (fat tails). 1 in 100 year floods happen every 30 years, to give a recent example. The number of major market crashes is way larger than almost all models suggest.
When you use leverage you increase your risk. There are no if or buts about that. The more money you have exposed to any market the greater your risk. If someone really believes they have the answer to increased returns without increased risk then heck they should go see GS and get paid seven figures, which is a geat reward for no risk!
Saying that I am a fan of intelligently used leverage. I can't speak to day trading, but as a long term investor there are times when the market is clearly cheap and times when it is clearly expensive, those times are rare and most of the time the market is neither. When it is clearly inexpensive then the time to use leverage is upon you, at that time most people will be selling and headlines will be terrible. When the headlines are great then it's time to raise cash. There may be good examples of using leverage in day trading, I'll have to leave that to others.
Circling back to the string of large numbers and a zero. Jesse Livermore and Donald Trump are both great examples of that, at the same time they show you that if you're not afraid of going bankrupt that the excessive risk along the way can be fun and give you a lifestyle you may seek.
YMMV.