Relief

I heaved a huge sigh of relief.

I felt as if a (colossal) weight had been lifted off my shoulders.

All the tension in my muscles eased instantly.

They heaved an audible and collective sigh of relief.

Assured that everything was fine, I could finally unclench my fists and relax my shoulders.

The creases of worry vanished instantly from his face when he heard the good news.

The butterflies in my stomach finally dissipated.