How to hold in tears?

The other day at the temple, my entire family came to me and asked if I could speak at my Uncle's funeral. They chose me because they know that I loved him like a Father and I have many great memories with him that I can share. As much as I love my Uncle, I just don't know how I would be able to do this. Every time I start to talk about him, my tears just start to stream and I don't want to fill the room up with even more tears. Also, I don't think people would understand much of what I'd be saying... especially when I'm crying. I won't let my Uncle down though. Right now, I'm just trying to figure out how to hold my composure and hold back tears when speaking. I do have many memories that I would love to share with the rest of the family and I need to make him proud. I must.