If youre losing lane badly

some lifesteal may prove just as useful as resistances while still giving you that damage item. Just be sure to sustain up between your fights. and go for quick short trades.

A friend of mine once said that you're supposed to build damage when behind.

I was pretty speechless.

Some champions are better off building damage than building resistances when behind. But if you are a top laner, typically you build resistances if you are behind or you roam for kills to catch back up and still build offense.

You really can't afford to stay in lane when you are behind AND still build offense.

You can build offense if you farm under tower and KNOW you outscale the opposing champion.

In general, you should adapt your build to the lane. I main top but I still mostly build defense early in general.