Hey, don't be so hard on yourself!
A lot of people on here (myself included) have taken breaks from aikido, or left and come back.
BTW, you'll be surprised how much weight you can lose with vigorous training in Aikido, especially with some minor tweaks to your diet (mostly just bumping up vegetables and reducing meat). I lost about 15 kg in 6 months by going to practice for 1-3 hours a week, and eating better. Probably won't lose as fast as other activities, but you really can lose it with Aikido as your main exercise.