There should be no such thing as "I don't know what to do with my life." Scratch that statement away and erase it, as it should be "I will aid the development of life extension technology until I do know."
It should be no surprise to anyone that many, or perhaps even a majority of people at any given time have no real idea as to what they want to do with their lives. No vision, no grand dream that captures them, no burning desire to achieve a specific great work. That isn't because they are incapable - far from it, it is because they haven't found their own personal blue touch paper yet. The space of ideas and ideals is vast, and even the most aggressively autodidactic internet-addicted polymath cannot embrace more than a fraction of the sphere of human knowledge. Yet you cannot know your grand vision, the one that resonates with everything your life has led to up until that point, if you never encounter its roots.
Which is where we come back to time. We tell the younger folk that it doesn't matter if they don't know what they want to do with their lives, as that knowledge will come with time. The rituals and mythology that spring from the passage from childhood to adulthood, repeated billions of times over the course of history, are as much about expanding horizons as they are about anything else. In our comparatively wealthy modern society, that process of expansion doesn't have to stop when you stop growing in body - except for the fact that we are all limited by the realities of the human condition, and aging in particular.
Our lives have a timer, and we are all well aware of it, for all that many of us prefer not to think about it at all. The whole structure of life and society revolves around the existence of that timer, as it ticks away the freedom we have remaining in which to find and work on something worthwhile. The rush to find meaning in life? There because we don't have enough time. The need to save for retirement and medical costs? The timer again, ticking away our health and ability to fend for ourselves.
When you cannot see even the first shape of what will be your life's work, and time is ticking away, the best thing you can do is to offer a helping hand to those who work on making more time - scientists, advocates, and others who support research and development of rejuvenation biotechnologies. You can do that at the same time as you search for the cause or idea that truly speaks to you, and it beats slumping back into the grey doldrums that seem to afflict so much of our society: people who never found that fire inside, and who have no time left in which to do so.
You have an option that the older folk of previous generations did not: you can help make more time for everyone, more health, more years, and time enough to find meaning in what you do.