When you talk about your personal wealth you are of course talking about your holdings of your country's currency - the same currency that you pay taxes in. If there were no state, there would be no currency, hence your 'wealth' could not exist. It's therefore wrong to say that the money you pay in taxes belongs to you. The government sets up the system of currency which allows you to earn money in the first place. You can't opt into that part of the system and then opt out of the other part where you pay tax.
RE: Why taxation is theft