Have plan and make an analysis for the best coins that you want to include in your portfolio. Some coins are moving differently and its normal, you dont have to worry about it as long as the coins that you chose to hold are well-established and unlikely to be delisted in exchanges. Invest a high portion to a coin that most investors trusted the most (BTC), then choose some alts that has high potential. For me, the purpose of diversifying is I have many coins to rely on that can give me profit, less risky and reliable.