Lets talk a little Math: lets say you are a good player. You're in the money, lets say... 65% of your SNG games. When you take the 10% rake into consideration, you ends up with minor winnings.
We all know those good days and bad days periods (there is a sentence in Arabic: "yom asal, yom basal" - one day honey, one day onion). Basically those rake will take you back to the 50%-55% zone.
Most online poker sites limits their rake in cash games to around 3$ per hand. If you'll play high blinds table (5$ 10$ blinds and above) it will make the rake insignificant. (and don't forget that rake in cash games is 5% and SNG rake is usually 10%).
For me, I have problem with cash games - I never leave the table when I should. Even if I set rules for myself, I always break them... but that's me. You should check what's your favorite game type and stick to it.