If you are considering tackling any graduate program, it is vital to reflect on how (and if) this endeavor will help you achieve your goals, both short and long term. Another important query to sit with is whether or not you have the capacity to delay gratification and the drive to keep going when things are overwhelming and the light at the end of the proverbial tunnel is ridiculously distant. The journey is a difficult (and expensive) one even without children; if you cannot answer these things you may want to wait. At the risk of sounding cheesy, you may want to ask yourself "what is my motivation?"
Research on creativity suggests that intrinsic motivation holds you longer and will see you through the difficult periods more effectively than extrinsic motivation. This is true for artistic creativity, but also for intellectual endeavors. Basically, if you are in this for extrinsic factors such as $$ or status you are less likely to persevere or be as effective in your work. Even worse, you are more likely to get burned out and disillusioned, which partially accounts for the relatively high rate of non-completion in PhD programs. Intrinsic motivation, however, is fueled by a sense of passion; it inspires curiosity and creativity not only in your work but in how you manage to navigate the challenges along the way. This is the stuff that moves you forward. So you have 200 pages of highly intellectual and technical (and probably dry) reading for 1 of your 4 classes this week... no problem, the discussions with your classmates are very stimulating and there is an underlying desire to share perspectives and ideas that makes most of the reading feel worthwhile on at least some level. A 20 page paper... can do; you wanted to look further into the relationship between two constructs and this is a great excuse to go there in depth.
One problem inherent in graduate study, even for those whose primary motivation is intrinsic, is the unavoidable evaluative component. Evaluation is a necessity, but it adds an extrinsic motivational factor. The natural flow of the process is altered, anxiety rises sharply, and the directions you go in may look different because you are meeting the demands or expectations of evaluators. I am not saying that it is necessarily a bad thing, but research on creativity clearly shows that the evaluative component has a negative impact on quality, productivity, and enjoyment of any activity - even the one you naturally gravitate towards.
Whether you create poetry, sculptures, mathematical equations, or original research projects there is an element of creativity that drives the process. In order to remain creative and manage the high demand and pressure while maintaining buoyancy and flow you have to return to yourself. There are countless questions you can ask in order to explore this. What drives you to engage in a project? What does it mean to do it? Where does it stem from? Where might it take you? The point of these questions is not to look at external factors (i.e. I might get a cool publication out of it), but rather to look inside yourself. Academia is inherently evaluative, and naturally gives rise to the challenges associated with extrinsic motivation. Intrinsic motivation requires nurturing in this environment. Balancing the two demands finesse. Know your professors expectations and demands (as well as their quirks), but also know yourself.
So, what is your motivation?
