It really really does depend on what you are doing though. If you are holding or trading super long term then for sure, sideways is buying time, but not too much too or you got nothing left when the real dip happens. On the other hand, if you are a short termer then you keep wanting to make money from volatility even during sideways market periods.
Stick to the plan, if Plan A never works then we have to proceed with Plan B or else, we have to set for another Plan as the situation is also changing. Either be a short-term or Long-term trade, it also depends on the market trend. We need to be flexible as we never know the trend of the market but more possible it is certainly moving up and down, and as a trader, we have to analyze it otherwise our trade will end up in losses and failure.
You kind of contradicted yourself though with stick to the plan,,, which negates the need for Plan B;)
The only true Plan A that will always work is dollar cost averaging, in which case, you are not even a trader anymore but a long time investor/hodler.
But if you are serious about trading, you cannot afford not to have Plan B or C even!