<human>: Give me the gist of the text in a nutshell

My boyfriend is a wonderful man and good at most of the things he does. However, he bounces back and forth between being incredibly self deprecating and self aggrandizing. I think the latter is done sarcastically due to his tone of voice. He tends to be a funny, dismissive man, and most people laugh at his behavior, but I feel like this just encourages him putting himself down. 

As his SO, I wouldn't want to just laugh off this behavior. However, I'm a very confident person at heart and don't know how best to respond to my partner when he says certain things and behaves in certain ways. Have any of you been in a relationship like this? How is the best way to respond to show your partner that you care about them and think that they are wonderful and deserve to have high self esteem?
<bot>: Boyfriend makes self deprecating statements and I want to figure out the healthiest way to respond to these statements.