There is no greater path to wealth accumulation than owning stocks, and I've been buying up pieces of companies that I think will be worth more in the future for more than three decades. Building a portfolio is never an exact science, and sometimes rising stocks or taking advantage of pullbacks as buying opportunities can lead to oversized positions in some of your investments. My three largest stock holdings are Netflix (NASDAQ: NFLX), Walt Disney (NYSE: DIS), and Ambarella (NASDAQ: AMBA). Why do I own them? Why did I let them grow to the point where they're the needle-movers in my portfolio? Let's dive into my reasoning, one stock at a time. Image source: Disney. Netflix Every investor has a story of perfect timing, and mine involves buying into Netflix when it was a broken IPO in the months following its 2002 market debut. Netflix was just mailing out DVDs -- and its biggest foes were Blockbuster and eventually Redbox -- when I bought in as a satisfied customer. I had no idea that Netflix would be smart enough to be its own disruptor, taking the lead in streaming subscription services that made its disc-based model obsolete. I couldn't imagine that it would be a major player in original content or dominate global territories. My investment in Netflix is a 417-bagger as of Tuesday's close, but the sad turn here is that I sold 90% of my stake way too soon. The stock I sold would be worth more than $972,000 today. There's a lot of regret in my top holding, but obviously I'm glad I kept 10% of my original 2002 position. Walt Disney The family entertainment giant is the first stock I ever owned, a gift of a single share from my girlfriend back in 1986 (I would go on to marry her, of course). I wasn't active in adding to my position, afraid to mix investing with nostalgia. However, last year I sensed a buying opportunity when analysts were knocking Disney for its fading ESPN subscribers. There's more to Disney than just its sluggish cable properties. Disney's portfolio is armed with the 10-figure purchases of Pixar, Marvel, and Lucasfilm that have made it the top dog at the multiplex in recent years. Disney's theme park division is just getting started on a multiyear makeover that should lead to a big boost in attendance. Disney is a much better company than it was when its stock peaked two summers ago, and I am fine with my decision to buy big into a company that has sentimental value to me. Ambarella My third-largest holding is a chip company, but not just any chipmaker. Ambarella is a provider of low-power, high-def video compression and image processing solutions. I bought into Ambarella four summers ago with the stock in the mid-teens. I was attracted to Ambarella because its products were playing starring roles in the Dropcam surveillance camera I had in my home and the GoPro camera that my son was taking everywhere. Privately held Dropcam would eventually be bought out by Nest, and the action-camera maker wasn't public at the time. I bought into Ambarella as a coattail play. Thankfully for me, Ambarella has held up far better than GoPro. Ambarella's presence in dashboard cameras, security gear, and more recently drones and factory-installed automotive equipment have helped diversify its business. Ambarella stock has shed more than half of its value since peaking two summers ago, but it has more than tripled since my initial purchase. Its recent guidance was uninspiring, but I've learned to ride the stock's ups and downs. 10 stocks we like better than Walt DisneyWhen investing geniuses David and Tom Gardner have a stock tip, it can pay to listen. After all, the newsletter they have run for over a decade, Motley Fool Stock Advisor, has tripled the market.* David and Tom just revealed what they believe are the 10 best stocks for investors to buy right now... and Walt Disney wasn't one of them! That's right -- they think these 10 stocks are even better buys. Click here to learn about these picks! *Stock Advisor returns as of July 6, 2017Rick Munarriz owns shares of Ambarella, Netflix, and Walt Disney. The Motley Fool owns shares of and recommends Ambarella, GPRO, Netflix, and Walt Disney. The Motley Fool has the following options: short January 2019 $12 calls on GPRO and long January 2019 $12 puts on GPRO. The Motley Fool has a disclosure policy.