Such thought patterns can equally easily lead further into depression. Indeed often one needs a motivating goal to get out of a depressive phase and as soon as everything becomes "meaningless", then no goal will be strong enough.
We have to find our own meaning and purpose in life, not look outside ourselves. I assume people reading my comment understand the distinction between higher purpose or meaning in the sense of the world at large, the universe, or the hereafter if you prefer, and what each of us finds personally meaningful or purposeful.
For myself, I found meaning and purpose from having children to raise. If I didn't have children I might find purpose in accumulating wealth, or finding a partner I enjoy spending time with, or traveling to see the world. Even hanging out with friends and laughing has some meaning, just not likely a cosmic meaning.
If a person needs to feel their life and (subjective) interpretation of their place and purpose in the world has importance and meaning outside of their subjective experience to stave off depression they should seek professional help. To imagine that what one does has significance, importance, and meaning beyond subjective experience seems like a symptom of delusion or narcissism.
I desperately yearn for a meaning/purpose to serve as a source of internal motivation…
Up until now, the only thing that has been a “motivation” for me is a fear of failure, so that’s what I rely on to get anything done.
I think the problem comes from expecting to find a larger purpose or meaning. Few of us will change the world significantly. Rid yourself of the idea that your life must have a greater purpose than satisfying yourself and the people you care about.
For example, too many people put a lot of effort into social media status in the form "likes" or "karma." What actual meaning does that have? What purpose does it serve, aside from attention-seeking and narcissism? When people spend their time on getting attention and status display their ego gets crushed when that attention doesn't come, or goes away. Wouldn't enjoying a walk on the beach give more pleasure, even if it serves no purpose beyond relaxation and contemplation?
You have to start with yourself, to find meaning and purpose for yourself in how you treat yourself, and then how you interact with other people. You can't start by hoping to find a greater purpose or meaning in life and feeling down and useless until that happens.