You actually have a positive impact. But you're also having a negative impact by spreading the mentality of "nothing will change", both to yourself and to other people you're voicing it to. It makes yourself and everyone you voice it to less likely to take action like you did.

Don't get me wrong, I also realistically believe we will run into massive problems. But the only sensible thing to do is just keep trying everything possible personally, it's the right thing to do.