I prefer weekly purchases because this increases the BTC owned, if this week does not buy BTC due to unstable cash flow then next week is double to make a purchase, I don't mind this being called aggressive in purchasing but I want BTC to keep accumulating every week.
One of the main points of the properly executed DCA strategy is regularity and consistency.
In theory, buying smaller amounts more often is preferable, as it should give you more protection from buying during exceptional spikes in price, but, in practice, it doesn't make that much difference whether you buy weekly or monthly.
If you're struggling with cash management and find it hard to stick to buying weekly, I'd switch to monthly purchases, especially if you're an employee and are getting paid every month not week. Should be way easier to manage.
Generally, the DCA strategy doesn't really requires struggling but rather it should depend totally on your cash flow and understanding how much of your disposal income that is readily available for investment, one doesn't really need to struggle but should tailor down the part that will suit him and give him that comfort to enable him make an informed decisions towards his investment, one of the important thing about the dca strategy is being consistent in order for you to have a good size of bitcoin over a long period of time.