[jiggi]

First of all, sorry if this is in the wrong place

I've recently started dating someone, and we've clicked so perfectly, we can both see a future together. The thing is, he's 20 and has a one year old daughter. In theory, I'm fine with it, I know she will always come first, and always be a part of his life. He's been broken up with the mother since before the little one was born. He's a good dad, and it's lovely to see.

I've never really been around children, but I met her this week, and I've helped look after her, and bonded a little bit. It's all been quite nice.
Then it all suddenly became overwhelming. I guess the reality of it hit me. I'm not even entirely sure what the problem is. it's just suddenly very hard to deal with. I really need to get past this, if I do spend my life with this guy, then I will always have his child there too.
Has anyone got any advice on how to deal? Or has anyone been through it? How long did it take you to adjust to there being a child involved?