Every so often in an investor's life, there will be a stock that you really want to own, but that you shouldn't buy. If you lack significant investment experience, or considerable willpower, you may be inclined to purchase the asset, potentially leading to future regret.For me at the moment, the stock I'm wishing I held in my portfolio is Palantir Technologies (PLTR 0.47%). Here's a look at why I'm interested in it -- and why I'm not buying it. Why do I wish I were a Palantir Technologies shareholder?There ...