Should I cancel my Endowment policy?

Why did you buy this endowment plan in the first place? Revisit that purpose/objective. $100 per month seems like a do-able sum, and can be a good form of savings (similar to RSP). If you cancel now, you will not get anything back. Hence, the loss from 5k is gone forever. Unlike for ILP, where you are covered during the period insured and you also get back a sum upon cancellation, for endowment plan there is no cash value due to early cancellation right?
Also, check on what is the rate of return you will get at the end of the 25 years. Is this a guaranteed rate? Can you beat this rate if you choose an alternative? This will be an important factor in your consideration.

Why do you want to cancel your plan?
Is it due to cashflow issues or there is an urgent need for money and that you cannot find any other alternative?

If that is the case, it does not matter what the return is because you need the money now.

However if you are cancelling it because you can get better returns elsewhere, then it is important to do your sum and take into account the time value of money and opportunity cost. (As Mr Hariz has mentioned above)

It is also good to have an endowment or a “guaranteed product” instrument in your financial portfolio.
It is not always about which give instrument gives the best return in the portfolio. Rather is is always about managing your risks and returns. Strategise it to your needs and goals. 👍🏻