Aikido training helps me understand myself better by pointing out fears, frustrations and also many good sides in me. I can then contemplate on them and see if any progress can be achieved on or off the tatami.
We train in correct breathing also which comes in handy in my meditation at home. I also found out that seiza is the only position for meditating in which I don't get a sore back (I have a problem with my spine and a certain muscle on my back - they both have gotten better since I started training though). And meditation certainly is one of the things I recomend to anyone interested in spiritual growth.