It is a combination of investment style, assets and strategies. This is essential in developing the faith to buy the fund, and to stick with it. Good investors write down their reasons for buying a fund. That list helps them maintain balance in the future, at times when short-term losses obscure sound reasoning. The research you do before you buy makes it a lot easier to assess a fund down the road.
Good investors save and invest under all market conditions.
You don't need to add constantly to each fund account, but you must invest regularly for the stock market to work for you. If you aren't saving and investing all the time, the best funds in the world probably won't earn enough to reach your goals. Spreading your risks to several asset classes or investment styles will smooth out the bumps in the market. But too many funds spoil a portfolio. Overall, you wind up with the rough performance of the index, minus the management costs of the funds.