If you think back your first times in Aikido class, what comes to your mind? What were the things that got you hooked up? Are they still there or have they changed during years somehow? When you think about somebody with large amount of muscle mass starting aikido, is there any advice you would like to give?
What is the one, the most important thing that aikido brings to your life, if you have to name one?
When I think back about the very beginning of my training, I think of the extreamly confounding nature of it. Beginning with my first observation of Aikido, which was skeptical, and extending from there i see a gradual shift toward understanding.
I hate to say it, but much of why I trained so much was born from unhappiness. I was depressed and living with a roomate who was a bit oppressive (a bigger personality than my insecurities could handle, at any rate). The dojo was a great environment filled with new friends and a stimulating set of ideas to consider. I've also always been very "spiritual" so it being a shrine attracted me as well. Now, those things are still there, but as I've grown these last nearly 10 years, the emphases have changed a little. Hard to describe how exactly except that I'm a little older and I feel less wise.
As for someone with large muscle mass, do lots of stretching is my only advice. I'm kind of the opposite to your situation: my upper body strength is fairly minimal. I've got strong legs from years of soccer and skiing, but my arms suck. It's forced me to rely more on structural strength, but that doesn't mean I haven't spent lots of time trying to muscle my way through technique like you described. Strong muscles help support your ligaments, etc. I can't see a problem with that, but I know many body-builders tend to be very tight and that can lead to muscle tearing and limited range of motion, so stretch lots to compliment your natural strength....per my opinion anyway.
If I have to name one, most important thing? Determination/sincerity. When I am as sincere a person as I know how to be, everything else seems to fall into place, regardless of how difficult it may be.
Cheers! And good luck!