Always, when starting a seed bead bracelet, necklace or earring, leave enough string/space for the clasps/ear wire. For example, on a square stitch bracelet I leave approximately 8-12" of tail to complete the ends.
This should accommodate adding the clasp, loop, or bead ending, double/triple looping through added clasp or ring beads required, and rethreading back into the piece to safely finish it.