When you are following an investment strategy and there is no instrument that meets your signal, you just have to hold on to the cash in your hand, even though you may feel like you must be missing out on opportunities to do a profitable trade.

Once you have determined how you wish to spend your time and what kind of opportunities you want to take on (investment strategy), you'll have to say no to seemingly good opportunities that don't meet your criteria. 

If you feel like you're missing out on a lot of good opportunities, then maybe it's time to revisit the strategy.

For example, if you have decided to take on only fully remote job opportunities, you have to say no to great offers that require you to come into the office. But, if you are having to say no to a lot of opportunities for this reason, it's time to revisit the decision to determine if it is an important enough criteria to pass up on everything that doesn't meet it.