Why is there the BitCoin limit? Because when the limit is reached we can't mine any BitCoins anymore 
And why would people then continue mining?
And why would people then continue mining?
If Bitcoin grows, then the amount of the transaction fees will be far larger in value than the mined coins.
If the fees remain small, then people will stop mining until it becomes much easier to find a block, and the miners that stay will be able to mine far more blocks than at present.
I dont get it? Why would I continue to mine bitcoins after the limit?
Because miners receive both the block subsidy (newly created bitcoins) and the transaction fees of all the transactions that they include in their block.
Keep in mind that we won't reach the limit for another 136 years. So unless you are planning on living a VERY LONG time, there will always be new bitcoins created for your entire lifetime. As the amount of new bitcoins per mined block is cut in half every 4 years, the value of the transaction fees is expected to increase. Eventually most of the miners income will come from the transaction fees (perhaps at that time we'll stop calling them "miners" and start calling them "transaction processors"? Regardless the function they perform will be the same).