Must try harder

For the first time in ages, a proper effort-based swim. 10 mins warm up, then a 1-8 pyramid, with 5s rest per length swum. Found it hard to stick to 30s per length, and was down to 31-32 or even slower (on average) on the long ones. But nonetheless, I did it. I think I should probably try and get back to 2 swims per week, but when?