I've sold horses because yes, I was bored, they didn't fit me, or they didn't fit my style or program.
The most recent two I sold was a 4 year old QH filly and a 15 year old TWH. The four year old was quiet, well trained, easy to catch, etc. VERY exuberant in the pasture, under saddle she was the calmest, quietest horse you could ask for. I, was so bored out of my mind I tried not riding her for several weeks JUST to get some excitement out of it!
Didn't work. Went to be a children's mount in an experienced home.
The second one was a previous rescue (starve case). BIG TWH, built almost like a draft cross. Very well trained, but with a bigger motor. Needed tuneup work, nothing major, really a fun ride. I sold him because he was older, and I did (and still do) have younger prospects to work with.
At the same time, I've recently purchased a colt with a very mellow temperament. He just accepts things well, first haltering was a breeze, handles extremely well, very people orientated. I like horses that are reasonable and mellow headed, but with a 'fun' drive.
If your looking for a higher-drive horse, I'd really suggest purchasing a foal from a higher-strung mother (the mothers temperament does have a big effect on the offspring), or an older horse all together.
My current five year old (going to the trainer on Monday to be broke!) was rather high strung as a youngster. Now, he's more mellow then my Friesian cross! Still spooky, but he just hasn't been taught any different. Just dozes off at the hitching post, very quiet to handle, no big, excitable drive.
Divo, my little pony on the other hand, is extremely easy to train, non spooky, and a pleasure to handle but can't sit still when standing tied. Just to much 'oompf', has a pretty big motor for his little stature!
I say if he doesn't fit, sell to a home where he does and find a horse that better fits you and your riding style.
Wait! I'll fix it....