You don't make feelings disappear - you simply change what you are feeling through your thoughts.
Depression and sadness are both feelings that thrive on thinking the same thing over and over again.
Find other things to think about. Start concentrating on each breath you take, how it goes in and comes out. Keep getting back to thinking about each breath, even if you get distracted, get back to that thought, even if you think it won't help.
It has helped me over the years.