>>2 and
>>3 have the gist of it.
1- Recognize the fact that the human brain is amazingly flexible and that it is totally possible for you unlearn the habit and solve this issue (have confidence: it also helps remove awkwardness).
2- Acknowledge that the form of your eyes are inevitable (genetics) and that visuals won't matter in a conversation if you give a good impression with the rest of your body language and words.
3- Recognize the moment you are looking down. Remind yourself you are speaking to someone and that someone would like you to pay attention to what they are saying and doing (and them).
4- If you look away, steadily refocus on the interlocutor (hand ->face -> eyes). You don't need to smile if you are not the smiling type of person, but avoid frowning.
The human brain would need around a month or so of conscious effort to learn these steps and turn them into a habit. After a few more moments of exposure, your body should instinctively follow through.