be like threading a needle

1. To pass through some small opening or passage (as a thread is passed through the eye of a needle). Getting through those hulking defensemen will be like threading a needle. Good luck! An angioplasty is basically like threading a needle—you insert a catheter into the patient's artery and move it through to the blocked blood vessel. I can't believe you avoided that obstacle with your go-kart! It was like threading a needle!

2. To require delicate care and thoughtfulness. Trying to motivate your students is sometimes like threading a needle—you need to strike the right balance of tenderness and intensity. Once you're a parent, it can be like threading a needle to protect your kids and also let them explore the world. You had to tell the CEO he made a mistake in his report? Woof, that's like threading a needle—how'd you pull that off?