I bet you have heard an excited, newly engaged person say something like: 'It's annoying when he just leaves me and goes out with his friends to the pub on Thursday nights, but, as soon as we're married, that's going to stop.' Or 'I have noticed how she flirts with other guys now but, once we're married, she'll change.' Or 'I know he drinks a lot while he is single, but he'll cut down when we're together.'
Those statements ring huge bells for any relationship because the expectations they contain are unreasonable, unwelcome and unlikely to succeed. This is because they blithely ignore the character, needs and aspirations of the other person involved. We all expect our partners to change without realising that, should they actually change into the person we desire, they might not like us at all! Moreover, we would no longer have any control in the relationship because it would be like dealing with a virtual stranger, one who is bound to expect something more than we can give. People who expect their partners to change into their ideal after the vows will be very, very disappointed, a situation which often destroys the relationship. If you are going with someone now who has an irritating habit, don't think that when you are married or living together it will get better. In fact, it is likely to get worse with familiarity. If it really bothers you, or you have doubts about your intended, don't go there!
You Can Only Change Yourself
The most crucial thing you need to accept is that the only person you can ever change is yourself. People change because they want to change, not because of outside influence, unless they wish to impress or copy someone they admire. Those entering committed relationships do change some of their actions, but they tend to be minor and align easily with their aspirations. It is difficult to change primary aspects of ourselves which form the core of our identity, values and beliefs, unless there is a major benefit in doing so. Furthermore, people rarely change when they are under pressure from someone else, even a loved one. In fact, that is the time they are likely to feel inadequate and will most resist any request to change.
Please note that the addictive behaviour of loved ones with alcohol, drugs or other substances are totally outside your control. Any change in such behaviour is almost impossible unless engineered by the person himself. Your love cannot cure her illness, no matter how caring you are. It will require professional intervention. Constantly hoping that a person will change, and nagging them to do it, will only make you feel frustrated and impotent and leave them feeling hassled. You may help your partner by providing information, making resources available, being supportive and seeking support yourself (for example, with Al-Anon), but it is up to him/her to work through their problem for their benefit.
In the end, the strongest relationships are based on the commitment of two independent individuals to encourage compromise, growth and change for both parties, not one person giving in to, or having to endure, the unreasonable demands of another.