Moral standards are a matter of opinion. In society, it's a "consensus opinion" and it's what keeps me from driving to the grocery store in my birthday suit (that, and the "morality/health laws" regulating dress codes). We all have a social contract with each other that enables us to live in close proximity to others without killing them (for the most part -- killing neighbors is still a fairly rare occurance).

I feel that I can make the above claim based on history. Up until a hundred or so years ago, it was considered "moral" for a man to own slaves and to beat his wife and children, as they were also "his property" to do with as he pleased. Even now, there are cultural practices in various cultures on the globe that are "amoral" or abhorrent to one group, yet are considered "perfectly normal" to the culture in which it is practiced (such as circumcision). The social contract is a living and fluid thing (as is the "consensus morality") and it changes over time, with the tastes of the society that enforces it.

Sorry to burst your bubble, but you ARE able to decide what is moral for you AND act upon it. And people do so every day. However, if you grate against the "social contract" (by acting in ways that are detrimental to those around you), there's a good chance that the rest of society will do something to get you to conform or to remove you from its presence (usually by enacting laws and then enforcing them).

Morality, like ethics, is a personal thing. It's not something you can legislate, and, despite what preachers may think, it's not something you can instill through fear. All you can do is "regulate behavior" that way.

As far as Truth goes, as long as we are observers of the universe, we will never percieve the "objective Truth". And we are designed to be observers.