Life is hard. No matter how much we try, a lot of things are just out of our control. Sometimes things in life happen due to bad luck or poor timing. We can't control those things. The only thing we can control is OURSELVES. So how can you prepare yourself to be able to consistently succeed and get everything you want out of my life?
I would argue that the best way to enjoy life and find success in anything you do is to create the proper mindset. That mindset would be one that is not dependent on outside, uncontrollable events, but rather derives satisfaction only from the things that you, as an individual, can control.
In essence, I am stating that a healthy detachment from outside, uncontrollable events is the key to maintaining a healthy, balanced mindset and lifestyle that will enable you to achieve success in your life. When you derive your happiness and joy from external events, you are vulnerable to the savage ups and downs that life throws at you. It's a constant roller coaster ride. According to the Buddha, the source of suffering is craving; in other words, this craving is the hunger for attaining joy or happiness from external events or other people. Remember, we cannot control the outside world. If we want to feel in control of ourselves, we must obtain validation only from ourselves and approach external events in a detached way.
What does this have to do with relationships? Simple. Often, we get into a rut where we seek to obtain our joy from another person, from the other person in the relationship. This is a recipe for disaster. No other person can make you happy- remember you can't obtain happiness from the external world. However, what happens is that when the other person is fighting or unhappy in the relationship or wants to leave, it devastates the person who is emotionally dependent and obtains their happiness from their partner. No person can be the source of happiness for another person. Also, it is too much of a burden to bear for the other person and that kind of neediness only serves to push the needy person away.
Remember, to be happy in life and lead a healthy relationship, you must never make your partner or anything else external as the source of your happiness. Look within and learn to develop a calm detachment from external expectations. You, and your partner, will be much happier for it.