It cannot be stressed enough that the objectives should be kept realistic. Your goal may be striving for a sustainable society, but like most goals, this probably will not be reached in your life time. Ideal goals are useful because you can never sit back and assume your work is finished, there is always more to be done. No one can ever tell you that we have reached sustainability and you can stop being active. If you keep your objectives realistic there is a good chance you will be able to achieve them.
Nothing is more empowering than reaching an objective.
For example if you organized a protest during the Gulf War there would have been a very small likelihood that it would have stopped the war. If stopping the war had been your objective you might have gone home from the protest depressed even if many people showed up. On the other hand if your objective was to create a visible show of opposition to government policy and to spread your opinions to many people, the same protest could be considered a success. This does not mean to say you should think small, just be realistic. Also to keep in mind besides realistic goals, is a realistic pace of activities.