1. Think of that block as a divine message to you. There's a reason you're struggling. Don't push it; don't force it.
2. Ask yourself, What is going on inside me that doesn't want me to write this? Fear of failure? Fear of success? Not something I truly want to do? I feel inadequate to write it?
3. Listen carefully to your heart's answer. Be compassionate toward yourself. Several times in my career, I've dropped projects (which wasn't easy to do) because, deep inside, I knew I didn't want to do them.
Here's one of my maxims:
Professionals write even when they don't feel like it.
I'm a professional.