Setting goals - again

I read about other people like Egomaniac Idai, who are a true inspiration.   He has just completed London to Edinburgh and back to London on the Elliptigo - 900 miles in 5 days, yes only 5 days and he had a couple of hours to spare!!  Unlike cycling there is no saddle so its standing up all the way all day.  You can follow him on Facebook.  Closer to home Eddie Grant who completed the Marathon des Sables - check it out a marathon of 150 miles in the Sahara in 6 days. It amazes me that they were sold out in one and a half hours of opening the booking.
I was a member of the Warrington Triathlon Club (and need to re-join).  They too have some inspirational people who are representing the UK in triathlons around the world. 
I would say that all these people have one thing in common, they set goals, achievable goals. They start small and build up.  I think that's where I have been going wrong, I am setting myself goals that are too big to start with.  I joined the gym to get myself started and didn't go.  I don't do classes at the gym so I set myself a goal to go to at least 4 classes a week, whether I was interested in them or not.
This week I have done 5 classes, Body Pump which was a disaster as I couldn't lift the bar over my head lol, two CX Worx which are core work, very hard but I did most of it. Pilates which I would like to try again once I lose my stomach, its hard to bend and breathe with a fat gut. I also did a tennis taster when I joined so I did a tennis circuits class, exhausting. I have four classes booked for next week and I will try and keep this up.  My main goal is to lose my stomach, but its a big goal.
My cycling seems to have come to an end as my left knee keeps giving way on me and I am getting left behind.  I now have my first aid certificate so I can do my own rides, but I don't feel confident any more.  I wouldn't want to get half way and not be able to finish.
I want to join the tri club again but just don't feel I am fit enough, I want to do a couple more tri's before I hang up my wet suit for good.  I will take a leaf out of Idai's book, he gets up at 5am and goes out training on his elliptigo.  I don't think I can do early morning as I have to walk Dolly first otherwise she would start barking and waking the neighbours, but, I can add an afternoon slot or early evening when its a bit cooler.  Or I could do the morning after walking Dolly.  Something to think about, but not for too long.
I guess goal setting is not my strong suit.