For Rilke, personal development is an organic process that should be allowed to take its own course. From Letter Three, in the Stephen Mitchell translation:
Always trust yourself and your own feeling, as opposed to argumentations, discussions, or introductions of that sort; if it turns out that you are wrong, then the natural growth of your inner life will eventually guide you to other insights.
Allow your judgments their own silent, undisturbed development, which, like all progress, must come from deep within and cannot be forced or hastened. Everything is gestation and then birthing. To let each impression and each embryo of a feeling come to completion, entirely in itself, in the dark, in the unsayable, the unconscious, beyond the reach of one's own understanding, and with deep humility and patience to wait for the hour when a new clarity is born: this alone is what it means to live as an artist: in understanding as in creating. In this there is no measuring with time, a year doesn't matter, and ten years are nothing.
Being an artist means: not numbering and counting, but ripening like a tree, which doesn't force its sap, and stands confidently in the storms of spring, not afraid that afterward summer may not come. It does come. But it comes only to those who are patient, who are there as if eternity lay before them, so unconcernedly silent and vast.
This is commonplace spiritual advice. And yet, so is “live for today”, the notion that if one were to die at midnight, every experience would be lived to the full.
Perhaps the paradox can be resolved through mindfulness, which is perhaps hardest of all: Live this moment to the full. Mindfulness follows from an understanding that one can only live in the present. Since one only lives in the present, there is no experiential time to be measured: you are always standing at the same place holding the tape measure.