It can be hard and things like potty training an go out the window when your first bring a baby home. I'm pregnant with my third and my daughter was only a year and a half when we brought our second home. I think it's a little different with and older kid and you might be able to talk them through things more. We got a doll for my oldest just before we brought the baby home and if had her old the doll and I'd have her hold the doll, comfort it, feed it, etc while sitting next to me when I needed to be with the baby which seemed to help. Also I thugs it was important to have individual time. Sometimes you need to run to the baby but sometimes you can saw things like "mommy will be right there baby, mommy' holding Kymber right now". Even if you only sit for another 30 seconds it can make the older kid feel like they're still important. Also roll with the punches a little even the best older sibling will likely hit (or whatever) the baby at some point. Don't sweat the small stuff...babies are more resilient than you think;)
My daughter just turned 2 last month. My biggest plan was to make sure my dd is potty trained.
I'm also on the same page with you I have a 3 year old daughter she is very attached to me. My biggest fear is how is she going to take it when her sister/brother is here. I'm due March 27th 2016 her 4th bday is on March 7
Number 2 will just fit into your routine, unfortunately when you used to have a break another child will be demanding your attention. My oldest daughter became a full on Daddy's girl and would tell me to go and be with baby. Really upset me! They ate now 3.5 and almost 2 and are becoming friends which is so lovely. I think at this age Eva is more able to understand than she was when we had Lexy. Not telling them yet tho!