Selena Gomez has had to ''learn'' forgiveness.

The 'Look At Her Now' singer tries to live by the rule ''Treat other people the way you wish you were treated'' and admitted the ''biggest lesson'' she's had is not to resent people who have hurt her the most.

She said ''The biggest lesson [has been] how to learn, [when it comes to] the people that have hurt me the most, to forgive them. And to continue to understand and have compassion for people.''

The 27-year-old singer admitted she was body-shamed after her weight began to fluctuate because of the medication she was taking to combat auto-immune condition lupus, which led to her undergoing a kidney transplant in 2017.

Speaking on her friend Raquelle Steven's video podcast 'Giving Back Generation', she said: ''I experienced [body-shaming] with my weight fluctuation for the first time.

''I have lupus and deal with kidney issues and high blood pressure, so I deal with a lot of health issues, and for me that's when I really started noticing more of the body image stuff.''

Selena explained that lupus doesn't directly affect her weight but a ''combination'' of different health factors do.

She added: ''It's the medication I have to take for the rest of my life--it depends on even the month, to be honest. So for me, I really noticed when people started attacking me for that.

''In reality, that's just my truth. I fluctuate. It depends what's happening in my life.''

And the 'Wolves' hitmaker admitted the comments really upset her and left her feeling ''messed up''.

She added: ''That got to me big time. That really messed me up for a bit.''