For whomever needs to hear this: prefer using loose leaf paper when sketching.

I have a big stack of printer paper I just pull from when I'm ready to draw. On my shelf are manilla envelopes to stash them in when I'm done.

Why? To keep the practice loose and free from the expectation of performance. There's nothing romantic about drawing on printer paper, it's cheap, and you won't feel the quiet pressure to keep performing at a certain level.

The bound sequential nature of pages means, in a sketchbook, if I had a great page, there's a quiet pressure to keep the bar high. Single pages have no continuity.

But! They can still be collected and organized into a stack. I, for example, have a stack of my figure drawing studies. And another stack for my perspective studies. If I wanted to, I could toss anything I didn't want to keep.

If the sketchbook is keeping you blocked and stiff, give single sheets a whirl.