It's fine to use your Ledger for regular transactions due to security reasons mentioned above, but I (and many other people) agree that it's always good to have a hot wallet with funds you plan on using for convenience. I occasionally send funds from my SegWit Ledger to my Blockchain wallet for use online, and it works just fine for regular use. I've had this setup for three years now (though I only got the Ledger Nano a year ago, I previously used an airgapped computer for cold storage), and I haven't been hacked or compromised yet.
As a reminder, fees are extremely low right now. It wouldn't be a bad idea to combine low/dust inputs and consolidate them right now for lower fees in the long run, and perhaps start a SegWit address if you haven't already to reduce fees in the long run in the future if things change.
Thank you everyone for your inputs and good advices. I found my Mnemonic pass phrase so I'm ok now...Green Wallet works quite well and the fee is pretty cheap ( I paid 6 cents for a $120 transaction - not bad - this is why we value bitcoin in the first place). Here's my reply to some other comments:
1). The $17 fee of a $12 transaction was not a large file - breadwallet was not Segwit compatible during the "high fee" period therefore they charge more (plus extra profits).
2) My bitcoin core full node is on a Mac computer - so I'm pretty secure here. One question: I've been running the full node 24/7 just to be a good bitcoin citizen for a while - but I'm not doing much to it and gain nothing from it. I've seen some " invalid transaction and connections errors" from the debug windows. Since I'm not too familiar with bitcoin programming (I need to do some more reading for this), I've switched off the connection for now until I gain some more programming knowledge and understand what to do with the core full node.
3). Yes I have already converted all my coins to Segwit address by just simply store my coins in Nano Ledger HW wallet.
Thanks,