Who can give me a hand?

If something is sensible, it makes sense, it is good practice, it is often a wise or clever thing to do. So sensible environmentalism is looking after the environment in a way that makes sense. I would say that this includes recycling whenever possible, things like tin cans and waste paper. The facilities are usually there for us to recycle nowadays and so it is good practice to make use of them. It does not matter if we care or not, it does not take a lot of effort to recycle many things. Do you mean sentimental environmentalism? If you are sentimental about something, your emotions are involved, you have strong feelings about it. So sentimental environmentalism would be taking action because you care about what happens to your surroundings. Perhaps you get involved in some sort of "green" organisation like "greenpeace". You would take your actions that bit further, because you have strong feelings about what mankind is doing to the environment. Hope that this helps. :)