Though I haven't practiced it as well as I'd like - yet - I "believe" in flat betting for these reasons.
- You should only be betting on things that you have a high confidence level in. The other stuff, you should mostly weed out without betting on at all; you should look for reasons to not bet on something. That would be instead of just assigning a low confidence level to those potential bets.
- we are often wrong about bets that seem so good. Over the long run those being wrong bets add up. Lessen their impact by betting the same amount on each wager.
- In an endeavor where being 60% correct over the long run is considered fantastic (and there is the juice), embrace the idea that winning bets (over the long run) is very difficult and that cherry-picking your "best" bets is well near impossible over time.
So yes, be much more selective and bet the same amount on each wager. Also, keep looking for sports where you have the best edge, even if it's something where you don't get the "TV game" often.