Hi Conny,
I recommend that you rotate the types of workouts you skip in each discipline. In swimming, cycling, and running, there are sessions that target low intensity (Z1-2), sessions that target moderate intensity (Z3), and sessions that target high intensity (Z4-5). Each week, eliminate one swim, one ride, and one run target each intensity level, with no overlap. The next week, do the same but shuffle things around so that you are never skipping a workout of the same intensity level in the same discipline two weeks in a row.
Coach Matt