Saving the planet - an enormous and incredibly complex task, will undoubtedly require quite a bit of individual action and behaviour change. To do without a straw or bringing your own cup can be a commitment to such behaviour change, to accept and act on whatever reasonable measure we find out to be important. Finding out that, say, producing a bamboo straw or cleaning the reusable mug takes more energy than producing plastic straws and cups should not be taken as a reason to mock well-intentioned actions (not saying that you did), but rather to iterate and figure out real solutions.