All the strategies are based on statistics.

To follow this strategy we need a win rate of 50+ % of the total number of bets. 
So we have to choose odds that in the long run gives us more than 50% success. 
I propose to bet on sports over-under between 1.40 - 1.70 at most, unless the possibilities of the result are better and also giving a high odd more than 1.70.
Let's built a random scenario which will give us at the end a 50% success.
We start with 200$.
We choose the unit we want to earn per winning bet. Let's say we want 5$ per bet.
Depending our choice, the odd is different. Let's assume that is stable and an average 1.57.
 
1. We open the built-in calculator and fill the boxes.
We bet 8.77$.
We lose. Now we have 200$ - 8.77$ = 191.23$ 
 
2. We open the built-in calculator again and fill the boxes including our previous losts.
We bet 24.16$.
We win. 37.93$. Real profit 37.93$ - 24,16$ = 13.77$ Now we have 191.23$ + 13.77$ = 205$
As you see with 50% success we earn our first target and all the previous losts.
Using the built-in calculator of the Betting Manager application, we follow the next step by step bets.
Now we start from the beginning.
We bet 8.77$
1.    Win    5$    Account : 210$
Now we start from the beginning again.
We bet 8.77$
1.     Lose    8.77$    Account : 201.23$
We write our losts.   8.77$.     Calculate the next.
We bet 24.16$
2.    Lose    24,16$   Account : 177.07$
We write besides our new losts   8.77$    24.16$
Now we lost twice. But in the next calculation we will not include all the previous losts. Just the previous one.(24.16$)  
That is because our bets are going to become too high and we don't want to raise the risk. 
We bet 51.16$.
3.    We win.    80.32$. Real profit 80.32 - 51.16 =  29.16$. Previous 24.16$ + our unit 5$.
Now we have 177.07$ + 29.16$  =  206.23$
We erase the last losts     8.77$    24.16$
Calculate the next, including the losts we didn't win back. (8.77$)
We bet 24.16$
4.    Lose    24.16$    Account :  182.07$
We write besides our new losts   8.77$    24.16$
Calculate the next, including only the last losts. (24.16$) 
We bet 51.16$
5.    We win.    80.32$. Real profit 29.16$. 
Now we have 182.07$ + 29.16$ = 211.23$
We erase the last losts     8.77$    24.16$
Calculate the next, including the losts that left. (8.77$)
We bet 24.16$
6.    We win.    37.93$. Real profit 13.77$. Now we have 211.23$ + 13.77$ = 225$
We erase the last losts     8.77$
And we start from the beginning.
You see that in the previous 6 bets we had 50% success.
 But we won every unit of 5$ per winning bet and we took back all our previous losts.

Depending on your account, you choose your unit per winning bet.
Remember that you may have better win percentage than 50%. 
These odds that verify the possibilities by themselves, will help you to succeed.
 
Betting Manager will help you to split your account and manage with discipline.
You may have a losing streak. 
If you work only with the available bank, you will safe the most part of your account.
Learn how Betting Manager works here.
 
Tip: If you have a losing streak and the stake become too high, split your losts to parts and try to win the parts. 
This is going to low the stakes. 
For example : We write besides our new losts   8.77$    24.16$
You can make it    8.77$    8.06$    8.06$    8.04$
Now try to take back the last lost (8.04)
Don't be afraid.
You will also have a winning streak too. 
Remember that the statistics and the possibilities work for you.