People invest for different reasons, with different goals and different motivations. Some think short term; others, long. Some may be planning for retirement or are seeking to preserve their assets in retirement. Many parents want to provide their kids with a post-secondary education. Others are simply interested in growing their assets. Who doesn't want to minimize taxes?
As is true for much else in life, having a strategy is key to achieving the outcome you want for your investments. You could take an ad hoc approach – making decisions on the fly – but having a plan is more effective for achieving your goals.
The question remains: Do you want to go it alone? Or do you want to get expertise on your side to help you devise an investment strategy that can work for you – no matter what you're investing for?