I guess I'll be the contrarian and say "it depends". I assume these are post-tax dollars you're planning to invest in a taxable brokerage account? If this is fully 10% of your net worth, are you sure there is no possibility you'll need to touch or access this money any time in the near future? Like, if you couldn't touch it for 10 years you'd be fine? You have an emergency fund? You have no debt? You have no short term obligations (taxes, etc)? Do you have a 401k? And/or an IRA? Have you maxed out tax-advantaged space?
Thanks for the advice. I will be able to invest in an index fund through a tax-advantaged space. So that's not a problem.
If I invest it, I will consider it untouchable for the foreseeable future and am confident in sticking to that, but I'd still rather not watch it achieve negative returns for a decade.
I should clarify, this would not be 10 per cent of my NW, but 10 per cent of my equity investments. In addition, I have an emergency fund made up of CDs laddered to ensure a supply of cash is available if needed. I have no debt, but no assets (like property) either.
If it influences anything, in the short-term I am also in a position to be able to save a significant portion of my net income, so I will have a reasonable amount to invest (or save) each month until at least the end of the year (approx. 5k per month).