hmm i would like to go a little more in depth than he did as I can understand your frusteration. I find myself in this conundrum in mid lane sometimes.
warding more often and in the proper spots. Top tri bush and river bush are your two go to. Try to purchase a pink at a certain point in the game usually when you back after your level 6 but before level 9. Use that in tri bush even if it gets discovered it still saved you from a gank. Also you could buy a green ward and ward the enemy top lane bush closest to his tower in certain matchups like rengar jungle for example. As some junglers like to lane gank. Keep your trinket ward for the river bush. And upgrade your trinket at lvl 9. This way you can use the 2ndary trinket ward to keep the bush nearest to his tower warded.
when you speak about demolished there could be many things wrong with what you are doing. So I will try to be generic overall to show where you can make easy improvements to help you.
Depending on when / how you are trading with the enemy in lane make sure when you decide to trade you have more minnions then he does in the creep wave. As this will allow him to take more damage and can change the outcome of a fight as the minnions will aggro on to him.
Back at the correct time. If your enemy laner decides to back you generally want to push the lane to his tower asap and back as well unless your low health wise when at that point you would just want to back and buy. This allows you not to have a lane disadvantage by him coming back with something while you are still with your base item. That will make you weaker than him and good players will know to take advantage of this situation and pressure you.
csing. With riven I know there is maybe a few times where you would want to all in the enemy but against many enemies in the top lane that could be ill advised. With riven lvl 3 would be a great time to assume some pressure on the opponent as you have access to all your skills.
Understanding your spikes. Sometimes disregard the point I just made before this one in certain situations. If you are going to hit level 2 before your enemy even if its by 1 creep you have two skills to the enemies one. This is a early game power spike that you can use to bully your lane enemy. Stay near a spot you know you can enter a trade with the enemy at and know how to use your CTRL + Q / W / E as this will level the skill its the hotkey for leveling a skill. This allows you to quickly level that skill and being using a skill such as your Q at basically the same time. This allows you to quickly react to your power spike by instantly trading with the enemy while your lvl 2 and he is still lvl 1. He will easily eat more than half his hp or even die due to this situation. Allowing you to freeze the lane and pressure the enemy away from CS without running the risk of dying or losing another trade that could result in his death. This will allow you to snowball your lane as you will be able to out cs your opponent unless he gets jungle pressure to stop the freeze. Or you finally push the lane back far enough that he feels comfterable farming. Also push him away as far as you can so he loses the experience from the creeps dying as well this will give you a level and exp advantage which again goes into spikes.
Itemization. Don't just build statically the same items all the time thinking they will work on every top laner. For example, if your fighting against AP you might wanna invest in a hex drinker. Also be sure to understand and react to what your opponent is or is not building. For example, if your opponent is not building armor pen items such as brutalizer; you may want to consider building a randuins omen.
Teleport use. Make sure you make good use of your teleport if you use that. Use it to eighter get a kill bot or mid when your top laner is backed and you have enough hp / dmg to attempt it. Or use it to secure dragon and help fight the enemy off it.
Hopefully this is a little more in depth and will be more helpful to you. I think I wrote enough for now though don't want this wall to get too long so enjoy