When setting objectives and targets for an Environmental Management System I see these same mistakes all the time.
1. Setting too many targets.
2. Setting targets that are unrealistic
3. Setting targets that you cannot have a direct influence on.
Firstly, you don't need to set targets for every environmental impact you have. You don't even have to set targets for all of your significant impacts.
My suggestion is that you pick a project each year. Select one area that you think you can make a difference in and put all of your effort into doing it well, rather than doing 10 half heartedly. You will meet the requirements of the standard and have a better result at the end of the year.