Read the dictionary definition of lighten. All definitions for this word.
1. alleviate or remove (pressure or stress) or make less oppressive
1. relieve the pressure and the stress
2. lighten the burden of caring for her elderly parents
2. become lighter
1. The room lightened up
3. make more cheerful through the use of color
1. The paint will brighten the room
4. become more cheerful
1. after a glass of wine, he lightened up a bit
5. reduce the weight on; make lighter
1. she lightened the load on the tired donkey
6. make more cheerful
1. the conversation lightened me up a bit