I am a member of the Federation of Dutch Trade Unions, or FNV, and they are not that progressive. They include the police union and don't make a stand for Palestine. They have made a statement today as a reaction to calls to kick the police union out of the federation. These calls came after police violence against pro-Palestine supporters. The leader of FNV defended the police union in his statement. I think the union has an important place in the fight against capitalism before, during and after the revolution. So when the union is compromised, it means it will be harder for change to happen. I do have hope for the union, but how can you exactly help bring back the revolutionary spirit and ideals?
Learn socialist history and theory in regards to political struggle, figure out if you are good at propaganda or agitation or find comrades that are.
Do what you can to teach others that unions can do more than just manage the worker/employer relationship and that it has a moral duty to use its massive body to act. Don't expect to fix anything on your own, but every little thing you can do paves the way for the next person who feels the same way you do.