This is quite an important question actually, because a certain amount of contentment is quite necessary in the meditation practice. And finding that balance between contentment in ourselves, content and understanding how fortunate we are with the practice and then not allowing it to go into complacency is important. It is a very difficult thing sometimes to recognize, it's the quality of being too tight or too loose. As we practice I would hope that there is much more contentment arising with ourselves and the feeling of a sense of refuge arising.
Complacency: if we find that we are starting to think that we are not going to die and that we have a lot of time left, we may be going into complacency. If we are starting to take our practice for granted, our development for granted, not really realizing how precious it is.
On the other hand there is a certain feeling that, "Wow, how fortunate I am, and how did it really happen?" A sense of wonder sometimes when you wake up and wonder, "how on earth did I get in touch with the Buddha's teaching?", and "how fortunate I really am". If this tendency is not arising so much in our life then we know we are getting complacent and starting to take it for granted. And then the energy does not come, as I said, energy and determination are often developed through a sense of confidence, "How is it that I have so much refuge when so many people in the world do not have it?"
If we are getting complacent, sometimes we're not looking out enough and understanding the amount of suffering in the world, and How Truly Fortunate We Are to have an inner direction and an opportunity to develop ourselves in this life. So, if this feeling - I can't actually describe it except saying "Wow, how did it happen?" - if that tends not to arise so much, then we are just taking the ease of the practice for granted, the ease of not having so much of the hindrances arising, the ease of having confidence in ourselves and others, even the sense ease in having spiritual friends, or spiritual teachers. If this sense of "complacency" overpowers this sense of "wow", then perhaps we are, indeed, getting too complacent.
If we feel we are getting too complacent, we need to read a few newspapers intensely, look at the Dukkha that is arising in the world, and ask ourselves a few questions like: "Would I have this opportunity if I was born in such and such a land, in such and such a position?" When we open out to Dukkha, some more Compassion for ourselves may arise to not take our precious opportunity for granted so much and get comfortable with the sense of ease, rather then getting the spur, the sense of urgency arising in ourselves.
This is why we often emphasize the reflection on death to give a feeling of "Samvega" or urgency to our practice. Because we are fortunate, but for how long? And when we have such good Kamma to have come in contact with the Buddha's teaching and have the precious opportunity, then we want to develop more of this sense of awe at our good fortune.