Chrissie Hynde gave up smoking marijuana because it was too much "hassle" to get hold of.
The Pretenders singer has known for decades that drugs and alcohol weren't good for her but only gave up around five years ago after experiencing a week-long hangover.
She said: "Drinking and drug taking impairs the quality of life. I realised that in my 20s but I never got around to fixing it until my 60s. The last time I got really wrecked was at Kate Moss' 40th birthday party. I was so ill for a week after I thought, 'That's enough.' I had many, many epiphanies leading up to that one, but that was the one that finally stuck. I've also even stopped smoking pot, cos it was too much hassle to get it. And if there's one thing pot heads don't like, it's hassle."
The 68-year-old star has been vegetarian since she was "very young" and admitted her meat-free diet has had the biggest impact on her life.
She added: "I became vegetarian when I was very young. Did people think I was weird? F**k them if they did. I never thought I was the outcast. There wasn't a specific moment that set me on that path, I just heard the word vegetarian and I thought about it for a while and realised that, despite my background, I could live that lifestyle.
"The vegetarian thing has informed my life more than anything else. Was it hard in the early days? No, it was not hard not to go into a Wimpy or a McDonald's."
The 'Brass In Pocket' hitmaker gets very frustrated when people don't stick to their plans.
She told Q magazine: "I'm not trying to be all sanctimonious but I find it incredibly rude when people are late. It's just a wind up. You made a deal, stick to it. You're not doing what you said you'd do.
"You can extend that to so many areas of life, like getting a band together. I've heard that so often. It comes from hanging out with too many cokeheads over the years. Cokeheads talk all night about their plans and nothing ever happens. I've become allergic to that."
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