don't be despondent. the key phrase in your post is "i feel i'm healthier than i've ever been". that is the main thing
losing weight is simple. as greg says take in less calories than you burn off. the question is how best to do this.
3 years ago i had a bad knee injury, the result of which was my weight went up to 14 stone 5 lbs. i still ate and drank like a 40 mile a week runner. my knee problems were diagnosed and i was put on a series of exercises. in 3 months i lost a stone, mainly through diet regulation, with an increased physical exercise but no runs of greater than 3 miles. within a year i was down to 12 st 2, but this was mainly due to increasing the exercise through further running of up to 40 miles a week.
my basic principles were
1. weigh yourself each week in the same conditions. don't try to cheat early on by not eating or drinking before weighing.
2. be disciplined in your eating. eat 3 meals a day, making sure that you have a good breakfast. i would eat a large bowl of meusli with natural yogurt and it set me up for the day. don't eat anything between meals if you can help it. if you feel hungry drink some water, often your brain confuses thirst and hunger. if that doesn't satisfy eat some fruit.
cut out non-essential eating and drinking - i gave up rubbish non-filling foods like crisps and sweets, although i would very occasionally have a bit of chocolate as a treat, and i stopped drinking at home. i would still go out but found that as i was losing the weight i would moderate my drinking to about a half of its normal amount. try to drink 5 or so litres of water a day - tap water stored in the fridge tastes as good as any bottled.
3. increase your general exercise routine by making changes to your habits. take the stairs not the lift, walk or cycle short distances rather than taking the car. exercise whilst doing other things: i have an old rowing machine that i would use whilst watching tv