its hard to actually describe the way you feel, but your right about a few things. i suppose its the feeling of not being complete without that other person. wanting to involve them in everything you do, to share the ups and downs with, the good times and the bad. wanting to make them feel special all the time and to protect them. aching for them when they are away, counting down the seconds till they return. thinking there gods gift and knowing they feel the same about you.
but then these are the things you feel when your falling in love, after a while things change, but not in a bad way. the honeymoon period is over and you settle into a comfortable relationship, you stop worrying about things and start working better together, you know your partner inside out and know what to do/say and what not to, there are less arguments and you no longer worry about the outcome of a fight because you know you can just talk it through.
oh i dont realy know i suppose love feels like finally putting the last piece of a puzzle in place