When is a value bet an arb?

I’ve lost a couple of account now and only within the first few weeks of placing about 6 bets a day. I checked a recent bet when it came up and it was indeed an arb showing 5 at bookmaker/ 4.95 on smarkets - which as we know can be underlaid for a profit.

Therefore my question is - how can we avoid taking arbs whilst continuing to take value?