᯽The eyes that were open᯽

To protect Rama and Sita during their 14-year exile, Lakshman didn't sleep at all.
Lakshman is said to have never slept during his 14-year exile to protect his elder brother and sister-in-law, for which he is also known as gudakesh (one who conquers sleep).
Nidra Devi (goddess of sleep) appeared to Lakshman on the first night of exile, while ram and Sita were sleeping and he quickly requested her to bless him so that he would never fall asleep.
Nidra Devi inquired whether he had anyone else who could take his place and complete the sleep of his share. Urmila, Lakshman's wife, was offered the opportunity to sleep. Devi Nidra asked Urmila if she agreed, after hearing this Urmila gladly said yes, completing both her own and Lakshman's share of sleep.

Note: this has been mentioned in the valmiki ramayan just in case you are confused