It's really quite simple: You no longer have the freedom to decide whether or not to have health insurance. If you don't purchase it, you get fined.
A few months back the following suggestion was
offered:
But Congress could address this problem more directly. The law could give people a right to opt out of the mandate if they signed a form agreeing that they could not opt in for the following five years. In other words, instead of paying a fine, they would forgo a potential benefit. For five years they would become ineligible for federal subsidies for health insurance and, if they did buy coverage, no insurer would have to cover a pre-existing condition of theirs.
The idea for this opt-out comes from an analogous provision in Germany, which has a small sector of private insurance in addition to a much larger state insurance system. Only some Germans are eligible to opt for private insurance, but if they make that choice, the law prevents them from getting back at will into the public system. That deters opportunistic switches in and out of the public funds, and it helps to prevent the private insurers from cherry-picking healthy people and driving up insurance costs in the public sector.
This avoids the problem the mandate is designed to address: people being able to game the insurance system by opting out until they need insurance, at which point they enter an insurance pool but face no discrimination for the pre-existing condition they've developed. Would such a model be acceptable to you? You get your choice back but don't have the option of passing your costs onto the rest of us in the process.