post-workout eating, I've been getting this wrong for ages

Right so I did a longer run on Saturday — about 45 minutes, which for me is a lot — and I came home and just had a cup of tea and a biscuit (gluten-free obviously) and wondered why I felt absolutely rubbish for the rest of the day. Tired, a bit headachy, legs like concrete on Sunday. Basically I've been ignoring the whole post-workout window thing for years. I always thought it was one of those gym-bro concepts that didn't apply to a normal person who just runs a bit and does a yoga class on Wednesdays. But I've been paying more attention lately and I think there's genuinely something in it? Even just having actual protein and some carbs within an hour makes a difference to how I feel the next morning. For me that's usually eggs on GF toast or sometimes I'll do a smoothie with collagen stirred in because it's quick and I can't always face cooking right after. I don't fully understand why it works, I'm not going to pretend I do — something about muscle repair I think — but honestly I've noticed it enough times now that I just do it. That's proper lovely compared to feeling destroyed all of Sunday.