A complex or compound emotion (I named it to have a name to refer to) is an emotional set that contains conflicting emotions at the same time or same timeframe.
For instance, you can love and hate someone. You can be wanting to spend your life with someone yet be extremely upset and hesitant to do so because of something they have done or are things they exhibit in their personality or actions. You could be happy to get your dream job but very sad that it is away from your fantastic family. You could be happy for a raise but sad because of the extra stress it exerts on you.
Be aware of these situations. Be aware because they are especially tricky when deciding if you want to be in a relationship with someone for a long period of time with someone. Marriage is the main focus of the wariness of this article.
Make sure that there is a for sure that someone wants to be with you forever but also that they have no doubts and if there are any that you are able to work them out. DO NOT FORGET THE DOUBTS PART.