I have a question about crushes and attraction.

From past experience and stories, I learnt that when a guy constantly looks at you, it means he's interested.
But I also learnt that when a guy wants a girl, he will go to great lengths to get her.
NOW, please explain to me, why my crush literally eats me with his eyes ( Today was probably the last day we will be seeing each other, and my friend said he looks at you as if he's seeing you for the first time, or the last time. ) But he does this siince quite some time. Then why didn't he take any step ? Or initiated anything.
Crushes are confusing.