How can I hold in my tears, when I want to cry so badly?

I don't like to cry in front of people and my parents are always fighting and sometimes it's hard for me to stay calm and pretend everything is fine like I have been doing for about the past 2 years. The fact is that I am depressed for too many reasons to name and lot's of times I just want to let out my pain, but feel the need to hold it in. Sometimes it's hard to just clear my mind like I usually do when I need to hold back my tears