Because I have a headache, I will lie on the couch for an hour.
Yesterday, because I had a headache, I lay on the couch.
Because of my headache, I have lain here for two hours.
Lay vs. Lie vs. Laid vs. Lain
Lie means “to rest oneself down.” The past tense of lie is lay, and the past participle is lain.
Examples
Lay means “to put or set something down” or “to put something in a resting position.” The past tense of lay is laid.
Examples
I am going to lay the quilts onto your bed gently.
Yesterday, I laid the quilts onto your bed gently.