Everyone has something that they want to accomplish or get better at or do more often, and no matter how much we think about it, it just keeps slipping by. Another opportunity to eat healthier or practice a certain piano piece, etc. is trumped by other priorities, other obligations.
Accept that this will happen.
You have priorities. Everyone does, and always will, that’s just part of human nature. Priorities that are higher on the list get done before those that are lower. Sometimes you have control over the priorities list and sometimes you don’t. Priorities come bundled with an inherent level of importance depending on your lifestyle and the elements you cherish.
Increasing the importance of a priority.
If you have something in mind that you have wanted to undertake, but have not been able to find the time for it, there is a way to increase the importance. Generally speaking the items that are a "bigger" part of your life get more attention - the house, kids, job, etc. So with this philosophy, if you make something a larger part of your life, it will inherently become more of a priority.
Make your priorities a hobby!
If you make something a hobby it will become more important to you because of the fact that it has become a larger part of your life. My wife recently became fascinated with eating healthy. She fed that fascination by learning about food from the bottom up. She studied hundreds of healthy foods, read books, blogs, labels and talked to other people with similar minds. She became immersed in this knowledge and has gained an invaluable understanding of what is healthy and why . She made this lower-level priority into a hobby that expanded and consumed spare moments that would otherwise have been used doing other things. Her other priorities didn’t necessarily have to wane to make room for it, but they were simply rearranged to accomodate for it.