A successful transaction should finish almost instantly. To know whether your payment failed or is stuck, you can simply look at your balance. If it failed, your balance will be the same as before the payment. If it's stuck, the amount of the payment will show as deducted from your balance, but won't be listed as a sent payment.
In either case, the cause is usually a lack of liquidity in channels between your node and the recipient. It's possible that one of the hops was halted by a power outage, or that particular node fried, but these instances are rare. The best course of action is to wait until the timelock expires and your funds are returned to your node. This can vary, but is usually about 144 blocks, or ~1 day. It's probably not necessary to reevaluate your connections unless you're experiencing multiple failed payments. Opening a direct channel with the party you're trying to pay may also solve this issue.