Do you feel you have worked harder than your horse at the end of a schooling session ? 
Do you feel like your kicking, squeezing to much and getting little result ? 
I have put together a few exercises that I have found effective when backing / bringing on horses over the years. 
Sometimes if you have a really laid back horse schooling more has the opposite effect. A lot of schooling does get boring, the best thing you can do is to mix it up a bit. 
Hacking / straight tracks is a brilliant way of getting your horse thinking more forward, if this isn't an option for you then straight line work in the school rather than circles as that is more hard work. You can work on transitions and getting your horse listening to the leg and seat, moving on and off the track from the leg, halt to walk transitions and gradually building up to trot / canter transitions over time. Its important that your aids are effective constant kicking and squeezing and taps with a whip will just make them numb and harder to undo later. Especially in early days of their education under saddle The best way is to ask, use your leg (avoid pony club kicks) if still no result, your schooling whip visible - still not listening maybe a tap of the schooling whip and the second you feel more forward movement reward that is the goal. Its important not to force head carriage as this can make them think backward, first you need a forward horse and later when working correctly and engaging from behind your horse will find his natural self carriage.   
I don't do a lot of schooling, I keep it short and sweet around 20 - 30mins including warm up and cool down and I do this  a maximum of 2 - 3 times a week and I find I get the best work from my horses this way. 
I go in the arena on those days with a goal and it's important to make sure its achievable for you and your horse for the level you are working at. Once we achieve what I had in mind for that session on that day more so when its something new I leave it at that rather than going round and round trying to get it perfect first time. 
If I'm riding a dressage test I go over parts of the test at home that we need to work on rather than riding it over and over again as sometimes that gets boring and I find sometimes they anticipate the ques and that's where unwanted habits happen. 
I do a lot of ground work more than riding, I find it is excellent for building/maintaining bonds and where I can I like them to have an understanding of what I ask on the ground first with voice aids and then I Introduce seat and leg aids under saddle later without my voice. Long reining has been brilliant for helping my gelding with balance, collection, transitions and straightness. 
If its possible and safe for you to go to the beach is a great way of getting your horse thinking forward with all the open space, not necessarily having a blow out every time as this may teach them to run in open space but schooling there in straight lines doing what you would in the school can be much more interesting and less hard work for them and once they understand you can transfer that to the school. 
If you have a local hunt you can travel to drag Hunts are brilliant for getting them forward, the general atmosphere and buzz usually gets every horse in the mood! And yet to know a horse that doesn't like it they seem to all enjoy it. What's not to love running with your friends and hopping some hedges. 
I think sometimes we need to remember they are horses not robots and like us they can have days where they don't feel like it, tired , health related issues so if you feel your working to hard try and listen to them and find another way. Consistency is key but we have to be careful not to be repetitive as it is better to avoid trying to undo a  ring sour horse and just taking that little more time and patience and in return they will give you their best. 
Rebecca Duke Horse