Good luck SillyPoohBear and you have a beautiful daughter btw. This will be number 3 for me and the 1 for my OH. So, I know what you mean about kids wearing you down.
However I always looked at it this way: The relationship between me and my wife should be second to none. I always try to make time at the end of my day to take the time to just focus on us. There is no reason we can't take the time out of our busy lives to spend 30 minutes a day together. I think it really helps to keep the relationship strong.
Good Luck on number 2! I really have enjoyed my kids and its nice to have a second one, my 2 are great at entertaining each other.