Congrats to all who have achieved the Two Comma Club and those working towards it. It takes a lot of being thrifty, patience and a lot of luck. I started investing when I was in my early twenties. Like some of the others reporting, every time I would get a raise, I would increase my contribution to my tax deferred plan. It's been so long ago, I doubt it was called a 401k plan. I'm now 69 and reached $1,000,000 in financial assets at age 55. I retired at age 61 and reached $2,000,000+ at age 68. This was accomplished on just an average salary. Several years before I retired, I made a little over $75,000/yr. The economy and our business wasn't in the greatest shape, so during the last 3 years of working my income did not increase.
In my case, I didn't follow the Boglehead philosophy of diversification. I was 100% in equities until about the age of 58 or so. In fact, most of it was in my company stock. You might say I lucked out using that strategy. I'm currently 48% equities (diversified) and 52% bonds. I intend to keep it around 50/50+/- through re-allocation, withdrawals, etc.
I made a lot of miss-steps along the way. At one point, I was down over $400,000 because of not being diversified; however, I stuck it out, never contemplated getting out and luckily the market came back at which point I started diversifying.
Good luck to all in your investing endeavors.