A friend of mine recently attended a meeting about the nascent anti-Trump movement emerging in the UK. When I asked her how it went, she replied, “It was nice. Like the old days.” She meant that the meeting was reminiscent of those held during the heyday of Britain’s anti-austerity movement in 2010 and 2011.

Back then I was oscillating between low-level office work and anti-austerity activism. It was an extraordinary and dazzling time to be an activist in London, the site of the biggest protests. Your circle of comrades was always expanding; every week there was a protest or meeting of some sort. It felt authentic and urgent — a movement infused with real vitality and power. In some ways, it was the best time of my life.

But if there are parallels between the anti-Trump movement and Britain’s anti-austerity movement, contemporary activists should be worried indeed. In the latter, yes, the movement was transformative and we did brilliant things, but ultimately, we failed. If the anti-Trump movement is to avoid the same fate, it must learn from our mistakes.