the martingale strategy really sucks, I'm better off using the flat betting strategy in all of my bets, I prioritize long-term profits rather than dreaming of big profits in a short time
That's a bit of a weird statement. Both strategies (flat bets and martingale) have exactly the same odds and in the long-run, your net result (profit or loss) should be exactly the same in both cases.
The only difference is psychological and depends on your discipline, e.g. in flat betting, it might be easier to stop and accept the loss.
Yup, nothing but the discipline that you will go to implement whatever strategy you are planning to use while playing,
both flat and martingale strategy have good potential outcome if you can stop at the right time.
It's more on your self-control, both winning or losing. You should have set the limitation that you will use to make sure that you will not be overstaying inside the house.
If you can do that, the chance is good for you to earn some decent amount out from your gambling.