Possible Trigger Warning (depression)

My husband and I have been trying for about a year now to have a baby (currently on our TWW, again). It seems like everybody around us is getting pregnant and having healthy babies but try as we might, we're just not getting pregnant. I was wondering how you hold onto hope for so long? All of my sisters are pregnant currently and my best friend just found out about a week ago that she's pregnant too. I'm excited for them, but it's hard not getting heartbroken about it. I know a lot of you have been trying for way longer with no success and I just don't understand how you cope with people you're close to getting pregnant. Amy advice would be greatly appreciated...I've pretty much lost all hope at this point and I'm worried that I'm starting to fall back into my depression.