Good companies, different results

I just scanned my portfolio quickly, and observed that Merck is as right now the biggest position in my portfolio. Since I bought it a little over a year ago, it has appreciated almost 40% and making it 9% of my total investment. I also bought 3M almost the same period, with a -2% return so far. I have to admit that I wasn't being patient at the time. I had cash and wanted to invest it. 3M wasn't cheap but wasn't overvalued either. Being a good company it was a safe buy. It did just that, a safe buy. I wish I'd stuck to what Warren Buffett preached "consider the cost of opportunities." the 3M buy had cost me other opportunities, like those other stocks when they were beaten down, or when 3M was beaten down. 3M is serverely beaten down right now. With earning increased over 17% over last year and remain the same price I bought it? What was a safe buy then has become an attractive buy.